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Rethinking U.S. Nuclear Diplomacy With Iran for 2025
October 2024
By Kelsey Davenport
U.S. President Joe Biden inherited the challenge of an unconstrained Iranian nuclear program and is poised to leave office with Tehran on the threshold of possessing nuclear weapons. Unlike January 2021, however, there is no straightforward path for Biden’s successor to roll back Iran’s nuclear program. Both the United States and Iran have acknowledged that the 2015 nuclear deal, known as the Joint Comprehensive Plan of Action (JCPOA), is beyond revival.1 Even if the deal could be restored, it is no longer a sufficient bulwark to guard against proliferation.
Despite Iran’s technical advances, a nuclear-armed Iran is not inevitable. Recently elected Iranian President Masoud Pezeshkian has expressed support for nuclear diplomacy and campaigned on the promise of lifting sanctions. Although Iran’s supreme leader, Ayatollah Ali Khamenei, sets the country’s nuclear policy, he appears to have given Pezeshkian a green light to engage. Khamenei said in August that there is “no barrier” to negotiations even as he warned that Iran should not trust the United States.2
The next U.S. president will need to move swiftly to engage Tehran because the door for diplomacy may not remain open for long. If Khamenei withdraws his support for negotiations or regional tensions push the Iranian government to determine that nuclear weapons or Iran’s nuclear threshold status is necessary for deterrence, it will be more challenging to persuade Tehran to engage in nuclear talks. Washington also will need a new playbook for reaching an effective, verifiable nuclear deal because Tehran’s advances over the past several years will require a different approach to reducing proliferation risk sustainably.
The New Nuclear Threat
The risk posed by Iran’s nuclear program has been growing since Tehran began breaching the limits imposed by the JCPOA in 2019, a year after U.S. President Donald Trump withdrew from the accord and reimposed sanctions on the country. The steps that Tehran initially took to violate the JCPOA restrictions and build leverage in response to U.S. pressure were quickly and fully reversible.3 Since 2021, however, Iran has invested in new, more proliferation-sensitive capabilities. This acceleration appears driven by a desire to gain political leverage and reach nuclear weapons threshold status.
As a result of these activities, Iran’s nuclear program today is fundamentally different when compared to the pre-JCPOA period. Key differences include a shorter breakout time, expanded pathways to nuclear weapons development, and gaps in monitoring. In terms of the rapid breakout issue, Iran’s research and development activities, particularly on uranium enrichment, better position it to produce weapons-grade material quickly. As of mid-2024, Iran could produce enough nuclear material for one bomb in less than a week and enough material for five weapons in about three weeks.4 The time frame to produce multiple weapons will continue to shrink as Iran’s stockpile of uranium enriched to 60 percent uranium-235, which is nearly the 90 percent U-235 that is considered weapons grade, grows and it installs additional advanced centrifuges, which enrich uranium more efficiently. This shortened time period increases the risk that Iran could try to break out between inspections of its enrichment facilities by the International Atomic Energy Agency (IAEA) or divert material to a covert location to complete enrichment to weapons-grade levels.
In addition to affecting the short-term proliferation risk, the decline in breakout time has longer-term implications. In the event of a new deal, the breakout time could be extended if limits were imposed on Iran’s uranium-enrichment program. Yet, Iran’s knowledge gains make it highly unlikely that any new deal could reach the 12-month breakout period achieved by the JCPOA. The United States will need to contend with the implications of a shorter breakout period and Iran’s ability to reconstitute its uranium-enrichment capacity more quickly as it considers the framework for a new nuclear agreement.
Meanwhile, Iran’s R&D activities over the past several years have diversified the pathways to developing weapons available to Tehran if the political decision were made to build a nuclear arsenal. For example, Iran now can produce weapons-grade uranium using fewer steps than was likely pre-JCPOA. Furthermore, Iran’s development of more efficient centrifuges increases the risk that it could set up an illicit, parallel program to produce weapons-grade material, a path called a “sneakout.”Although sneakout always has been a risk, Iran’s experience producing and operating more advanced centrifuges suggests that the country could pursue this option more rapidly and with less risk than was likely before the nuclear deal. A covert site with a smaller footprint that can produce weapons-grade materials more quickly decreases the likelihood of detection, making the pathway more viable.
Finally, there are the monitoring and inventory gaps. The JCPOA required Iran to implement voluntarily an additional protocol to its safeguards agreement, which gave IAEA inspectors more access to information and sites. The deal also allowed the agency to monitor every aspect of the uranium-enrichment program, including continuous surveillance of certain activities. This verification regime provided greater assurance that Iran could not divert materials to a covert program without swift IAEA detection and that any deviation from its declared activities, such as enrichment to higher levels of U-235, would be detected quickly. In February 2021, however, Iran suspended these more intrusive measures and now is implementing only the comprehensive safeguards agreement required under the nuclear Nonproliferation Treaty (NPT), which history has demonstrated to be insufficient in preventing proliferation.5
As a result of Iran’s decision to reduce monitoring, there is an increased risk that it could attempt to produce weapons-grade material at its declared enrichment facilities between inspections or divert non-nuclear materials, such as centrifuges, from facilities that are no longer inspected to a covert program. As IAEA Director-General Rafael Mariano Grossi stated in 2023, it is no longer possible to ensure that the IAEA is accounting for all of Iran’s centrifuges.6
Beyond the immediate risk of diversion, the monitoring gaps could pose additional challenges for verifying a future deal. The IAEA already has stated that it may not be able to reestablish reliable baseline inventories in certain areas, such as centrifuge components and uranium ore concentrate. If a future deal imposes limits in areas where the IAEA does not have a baseline, monitoring uncertainty could undermine confidence in implementation.
In addition to these technical challenges, Iran’s nuclear posture is shifting. Tehran always has denied illegally pursuing nuclear weapons, despite assessments by the IAEA and the U.S. intelligence community that it had an organized nuclear weapons program through 2003 in violation of its NPT commitments.7 Although Iran still does not acknowledge the pre-2003 weapons program, high-level Iranian officials recently have suggested that the government will rethink its position on nuclear weapons if security conditions change. Pezeshkian emphasized after his election that “Iran’s defense doctrine does not include nuclear weapons,” but the shift in doctrine likely will persist.8 It is unlikely that high-level officials would suggest repeatedly that Khamenei’s fatwa against nuclear weapons could be reconsidered without his tacit approval. For instance, Kamal Kharrazi, an adviser to the supreme leader, said in April that “if the enemy threatens you, you will inevitably have to make changes to your doctrine.”9 Kharrazi made similar comments several days later when he said that Iran has reached “no decision to build a nuclear bomb but should Iran’s existence be threatened, there [will] be no choice but to change our military doctrine.”
Further bolstering the threat that Iran could pursue a nuclear arsenal, Iranian leaders have emphasized that the government has the capabilities necessary to develop nuclear weapons. Prior to Kharrazi’s comments, the head of the Atomic Energy Organization of Iran, Mohammad Eslami, acknowledged that Iran has the technical knowledge necessary to build nuclear weapons, as did his predecessor, Ali Akbar Salehi.10
Even if Tehran does not cross the nuclear weapons threshold, it no longer appears to be using its nuclear advances just to create leverage in future negotiations. Iran’s threats to develop nuclear weapons in response to direct attacks or targeting of its nuclear infrastructure suggest it is using threshold status to deter aggression.11 The more Iran perceives benefits from retaining its threshold status, the more challenging it may be to negotiate a deal that moves Iran off the threshold. This shift underscores the importance of the next U.S. president moving swiftly to engage Iran and the importance of taking Iran’s changing security calculus, as well as its technical advances, into account when developing a new framework for negotiations.
Using the Lame Duck Wisely
Despite expressing support for restoring the JCPOA and nuclear diplomacy, the Biden administration has done little to slow Iran’s advancing nuclear program. Biden does not have enough time left in office to negotiate an agreement with Tehran, but his administration could still pursue deescalation to stabilize the nuclear crisis and reduce the risk of miscalculation. It pursued similar steps in 2023, but progress was derailed after the Hamas terrorist attack on Israel on October 7 and Israel’s subsequent invasion of Gaza.12
Pezeshkian’s support for engagement, however, may have reopened the door for diplomacy on the Iranian side. Iranian Foreign Minister Abbas Araghchi said on September 15 that Iran does not intend to wait until after the U.S. election to pursue negotiations. He suggested that Iran will pursue talks with other states, including European countries, if the United States does not want to engage. On the U.S. side, Biden’s decision not to seek reelection creates more political space for him to provide incentives if Tehran deescalates. In a deescalation package, the Biden administration’s primary focus should be on enhancing the monitoring of Iran’s nuclear program to reduce the risk of undetected breakout and diversion. For example, Washington could propose that Tehran negotiate an access agreement with the IAEA that would allow inspectors to visit nuclear facilities that contribute to the Iranian nuclear program but do not house nuclear materials, such as centrifuge production workshops. The IAEA has not inspected these facilities since February 2021 when Iran suspended the more intrusive monitoring arrangements put in place by the JCPOA.13 This additional transparency also would reduce the risk of the United States or Israel misjudging Iran’s nuclear advances or intentions and prematurely resorting to force.
In exchange, the United States could allow Iran to transfer additional funds held in foreign countries to the accounts set up in 2023 in Qatar that can be used to pay for certain humanitarian goods. Another option could be for the United States to allow sales of a certain quantity of Iranian oil. Both options could be facilitated quickly and reversed quickly if Tehran failed to meet its end of the bargain.
A deescalation package focused on limited relief in exchange for enhanced monitoring will not provide the wide-scale sanctions relief that Pezeshkian seeks, but it would give him an early victory without trading away aspects of the program that Iran views as critical leverage for negotiations on a more comprehensive deal. More transparency also would support Pezeshkian’s claims that the program is entirely peaceful and that Iran is willing to pursue a broader nuclear agreement.
A New U.S. Strategy
Irrespective of whether Biden negotiates an interim deescalatory package with Iran, the next U.S. president will need a diplomatic strategy that takes into account the realities of Iran’s advancing program, its shift in nuclear doctrine, and the credibility deficit Washington faces after withdrawing from the JCPOA in 2018, despite Tehran’s compliance. A new approach to negotiations is particularly crucial because Iran’s nuclear advances make a military option, which successive U.S. presidents including Biden have threatened to use as a last resort, less viable.
U.S. or Israeli military strikes always have risked pushing Iran to make the decision to develop nuclear weapons, and the country’s threshold status and shift in doctrine now increase the credibility of that threat. Furthermore, Iran has hardened and dispersed its facilities in recent years, making military strikes more complex and challenging.14 There also is a risk that Iran already has diverted materials, such as centrifuges, to covert facilities. Iran’s nuclear advances and its possible diversion of materials would make it easier for the country to reconstitute its program after a military strike. As retired U.S. General Frank McKenzie, former commander of U.S. Central Command, said at a gathering in April, military action is the “worst way” to prevent Iran from developing nuclear weapons. “The less you know about the problems and risks inherent in a strike, the more positive about its potential success one tends to be,” he said.15
Given these realities, diplomacy remains the best option for reducing the proliferation risks of Iran’s nuclear program in the long term. An effective deal can draw on aspects from the JCPOA, but will need to include several key elements as part of a new framework. The most critical element should be extensive monitoring and verification. The irreversibility of Iran’s knowledge gains, particularly on uranium enrichment, will leave Iran technically closer to developing nuclear weapons even if its nuclear program is subject to limitations under a new agreement. This proximity, coupled with the challenge of verifying that Iran has not diverted centrifuges or other material for a covert program, suggests that monitoring and verification measures will be even more crucial in a future accord.
In addition to requiring that Iran implement the additional protocol to its safeguards agreement with the IAEA and agree to intrusive monitoring of fuel cycle capabilities, including real-time monitoring of uranium-enrichment levels, a deal should prohibit certain weaponization-related activities beyond what was required by the JCPOA. The parties also should negotiate verification measures so the IAEA can assess compliance with the weaponization prohibitions. Furthermore, the deal could include specific steps that Iran will take to assist the IAEA as the agency seeks to close the gaps in its knowledge of Iran’s nuclear activities resulting from its decision to reduce IAEA monitoring and access in February 2021.
Beyond this, the United States and the European signatories to the JCPOA (France, Germany, and the United Kingdom) should support cooperative nuclear activities as an additional means of fostering transparency. As part of a nuclear deal or in a separate agreement, the United States and the European countries could agree to support the establishment of a nuclear security center in the region, for instance. Creating spaces for Iran and other states with established or planned nuclear programs, such as Saudi Arabia and the United Arab Emirates, to collaborate on regionally identified security needs would build ties among expert communities and provide greater insights into the trajectories of each country’s nuclear program.
A new framework proposal also must involve enrichment limitations, but the limits should be structured to shift the direction and drivers of Iran’s enrichment activities. Currently, Iran’s uranium-enrichment program significantly exceeds the limits set by the JCPOA and the country’s domestic needs. For instance, Iran is enriching uranium up to 60 percent U-235, despite having no domestic justification for uranium enriched to that level, and it has installed more than 50 cascades of advanced centrifuges. Despite the current program exceeding the country’s requirements for enriched uranium, Iran is highly unlikely to agree to limitations similar to those in the JCPOA, which allowed the use of only 30 cascades of its first-generation IR-1 centrifuges to enrich uranium to 3.67 percent U-235, a level suitable for nuclear power reactors. Those limitations were based on an assessment of Iran’s practical needs and the goal of a 12-month breakout period; they are no longer politically or technically feasible. Although achieving a similar 12-month breakout period in a new deal is not necessary from a nonproliferation perspective if the agreement contains stringent monitoring measures, a new agreement must extend the current breakout period and should prohibit more sensitive enrichment activities, such as enrichment of uranium to 60 percent U-235.
The United States could look at two options for restricting enrichment limits under a new deal in a way that provides a strong barrier to proliferation but is also acceptable to Iran. One option would be to support regionally negotiated limitations on uranium enrichment. The nuclear landscape in the Middle East has shifted significantly since negotiations commenced on the JCPOA. There is greater interest in civil nuclear energy and other peaceful applications of nuclear technology, such as nuclear medicine and nuclear applications in agriculture.16 Saudi Arabia, which has threatened to develop nuclear weapons if Iran does, also intends to enrich uranium domestically. To reduce proliferation risks regionally, Iran and the Persian Gulf states could agree to cap enrichment at reactor-grade levels and set stockpile limitations for uranium kept in gas form, which can be enriched to weapons-grade levels more easily.
An alternative to regional limitations would be for the United States to negotiate limits with Iran as part of a nuclear supply arrangement that would benefit both countries. The United States, for instance, could agree to purchase uranium enriched to 20 percent U-235 from Iran to meet U.S. domestic needs in exchange for Iran agreeing not to enrich above that level and to retain a limited stockpile in gas form. Iran could blend down any uranium produced in excess of that limit. The size of Iran’s enrichment program could be based on supply contracts and monitored by the IAEA.
Similarly, the United States, the European countries, or China, another JCPOA signatory, could agree to work with Iran on fuel fabrication, provided Iran limits quantities of enriched uranium in gas form and limits the overall capacity of its enrichment program. This supply-driven approach would provide Iran with additional tangible benefits that would be lost if it breached its obligations and would enhance transparency by forging further connections between Iranian and foreign nuclear communities.
Finally, there is the issue of incentives beyond sanctions relief. Iran will demand sanctions relief as a core element in any future deal, but the demonstrated U.S. ability to reimpose sanctions reduces the benefits that Iran will receive from the lifting of those measures. It is likely that the United States will need to put more on the table in a future deal to benefit Iran. In addition to studying the JCPOA experience and examining how to provide more tangible and durable benefits when sanctions are lifted, the next U.S. administration should consider additional, durable incentives that would be attractive to Iran. This could include encouraging greater direct investment in Iran, particularly from states in the region; exempting certain regional trade from sanctions;17 and guaranteeing support for cooperative nuclear activities that do not pose a proliferation risk. Nuclear cooperation projects would be specific, required commitments for the United States and other parties to the deal, as opposed to the voluntary ones in the JCPOA, and could include assistance with developing fuel fabrication in Iran, expanding medical isotope production, and constructing proliferation-resistant power reactors. These activities would be consistent with Iran’s nuclear goals.
Sustaining an Agreement
If the United States and Iran can reach a nuclear agreement, the next U.S. president will face challenges in sustaining support for the accord, particularly through presidential transitions. A new strategy should include steps to mitigate the risk of a future president withdrawing from an effective nuclear deal, as Trump did.
In Washington, the JCPOA experience highlighted that a transactional nuclear agreement likely will be held to a transformational standard. Although the 2015 nuclear deal was never intended to be a panacea for all the problems in the Iranian-U.S. relationship, it still was criticized for failing to address other key U.S. concerns about Iranian activity, particularly the country’s growing ballistic missile program and its support for regional proxies, namely Hezbollah, Hamas, and the Houthis. When Trump withdrew from the JCPOA, he described it as a failure because it did not address these other issues.18
Negotiating a grand bargain between the United States and Iran would be far more difficult and time-consuming than the JCPOA negotiations. The immediacy of the proliferation risk argues for prioritizing a dedicated nuclear deal. Yet, the next administration should situate its approach to nuclear negotiations within a more comprehensive Iran strategy to demonstrate U.S. intentions to address a broader array of concerns. This strategy could include U.S. support for regional security talks, separate channels for Iran and the United States to discuss issues of mutual concern, and security assurances to U.S. partners in the region. The conclusion of a nuclear agreement should not be tied to addressing these other concerns successfully, but a more comprehensive strategy would demonstrate that the United States is actively engaged on these issues, increasing the likelihood of sustaining an accord. Supporting dialogue between Iran and other states in the region regarding the security environment is particularly critical because Iran is more likely to agree to nuclear restraints if it assesses that nuclear weapons or a threshold status are not necessary for national security.
In addition to developing a more comprehensive engagement strategy, the United States needs to bolster nonproliferation norms writ large and demonstrate strong global support for preventing the spread of nuclear weapons. The group of countries that negotiated the JCPOA (China, France, Germany, Russia, the UK, and the United States) was important in demonstrating to Iran the strength of the nonproliferation norm. Unfortunately, that model is no longer viable for negotiations. Russia’s blatant rejection of nuclear norms and failure to hold Iran accountable for safeguards violations demonstrate that it is no longer committed to upholding the nonproliferation and disarmament architecture. This break in unity among the JCPOA parties on nonproliferation has ramifications for Iran: if Iran believes it can flout its obligations with impunity and trusts that Russia will block any punitive action at the UN Security Council, Iran will be under less pressure to negotiate.
China, however, has an interest in preventing erosion of the nonproliferation regime. Beijing appears reluctant to use its leverage in Tehran to stabilize the current nuclear crisis, but it may be willing to reinforce nonproliferation norms more generally. If these states were to express shared concerns about certain civil nuclear activities relevant to weaponization or articulate the consequences of a state withdrawing from the NPT or weaponizing a civil nuclear program, it could help demonstrate to Iran that it will face costs for developing nuclear weapons.
Despite the collapse of the JCPOA, diplomacy still stands the best chance of preventing a nuclear-armed Iran and providing assurance that the country’s nuclear program remains on a peaceful trajectory. Concluding an effective, verifiable accord will be more challenging than ever given Iran’s nuclear advances and diminished U.S. credibility. If the next U.S. president moves swiftly to signal support for negotiations and embeds nuclear talks within a broader strategy to reduce Iranian-U.S. tensions, there is a chance to reach a deal that reduces proliferation risk, benefits Tehran, and contributes to regional stabilization.
ENDNOTES
1. “Exclusive: Iran Indicates ‘JCPOA Not Good Enough for Us Anymore,’” Amwaj Media, August 26, 2024, https://amwaj.media/article/exclusive-iran-indicates-jcpoa-not-good-enough-for-us-anymore.
2. Eve Sampson, “‘No Barrier’ to Nuclear Talks With U.S., Iran’s Supreme Leader Says,” The New York Times, August 27, 2024.
3. Julia Masterson and Kelsey Davenport, “Restoring the Nuclear Deal With Iran Benefits U.S. Nonproliferation Priorities,” Arms Control Association Issue Brief, Vol. 13, No. 1 (March 15, 2021), https://www.armscontrol.org/issue-briefs/2021-03/restoring-nuclear-deal-iran-benefits-us-nonproliferation-priorities.
4. Valerie Lincy and Gary Milhollin, “Iran’s Nuclear Timetable: The Weapon Potential,”
Iran Watch, June 27, 2024, https://www.iranwatch.org/our-publications/articles-reports/irans-nuclear-timetable-weapon-potential#10.
5. Trevor Findlay, “Looking Back: The Additional Protocol,” Arms Control Today, November 2011.
6. Jon Gambrell, “UN Atomic Chief Backs Nuclear Power at COP28 as World Reckons
With Proliferation,” Associated Press, November 30, 2023.
7. U.S. National Intelligence Council, “Iran: Nuclear Intentions and Capabilities,” November 2007, https://www.dni.gov/files/documents/Newsroom/Reports%20and%20Pubs/20071203_release.pdf.
8. Masoud Pezeshkian, “My Message to the New World,” Tehran Times, July 12, 2024, https://www.tehrantimes.com/news/501077/My-message-to-the-new-world.
9. Beatrice Farhat, “Iran Warns It Will Change ‘Nuclear Doctrine’ If Threatened by Israel,” Al-Monitor, May 9, 2024, https://www.al-monitor.com/originals/2024/05/iran-warns-it-will-change-nuclear-doctrine-if-threatened-israel.
10. Toby Dalton and Ariel Levite, “Iran’s Nuclear Threshold Challenge,” War on the Rocks, May 23, 2024, https://warontherocks.com/2024/05/irans-nuclear-threshold-challenge/.
11. Eric Brewer, “Iran’s New Nuclear Threat: How Tehran Has Weaponized Its Threshold Status,” Foreign Affairs, June 25, 2024, https://www.foreignaffairs.com/iran/irans-new-nuclear-threat.
12. Humeyra Pamuk and Daphne Psaledakis, “U.S. Says Iran Cannot Access Its $6 Billion in Qatar Any Time Soon,” Reuters, October 12, 2023.
13. International Atomic Energy Agency Board of Governors, “Verification and Monitoring in the Islamic Republic of Iran in Light of United Nations Security Council Resolution 2231 (2015): Report by the Director General,” GOV/INF/2021/13, February 16, 2021.
14. Jon Gambrell, “An Iranian Nuclear Facility Is So Deep Underground That U.S. Airstrikes Likely Couldn’t Reach It,” Associated Press, May 22, 2023.
15. Global and National Security Institute, “GNSI Policy Dialogues: The Iran Enigma - General (Ret) Frank McKenzie Featured Remarks,” YouTube, April 24, 2024, https://www.youtube.com/watch?v=kgJzDXhWfdw&list=PLm9bckPQyMTohGAbdty7uPx0dpzTppEyJ&index=3&t=701s.
16. Sarah Ruth Opatowski, “Development and Cooperation on Nuclear Research and Energy in the Middle East: Workshop Report,” UN Institute for Disarmament Research, n.d., https://unidir.org/wp-content/uploads/2023/09/UNIDIR_Development_and_Cooperation_Nuclear_Research_and_Energy_Middle_East.pdf.
17. Ali Vaez and Vali Nasr, “The Path to a New Iran Deal,” Foreign Affairs, May 8, 2023, https://www.foreignaffairs.com/iran/path-new-iran-nuclear-deal-security-jcpoa-washington.
18. “Remarks by President Trump on the Joint Comprehensive Plan of Action,” The White House, May 8, 2018, https://trumpwhitehouse.archives.gov/briefings-statements/remarks-president-trump-joint-comprehensive-plan-action/.
Kelsey Davenport is director for nonproliferation policy at the Arms Control Association.