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While persuading Iran to roll back its nuclear programme at this stage may be difficult, the US and its allies can and should seek to reinforce Tehran’s perception that a decision to weaponise the programme would increase Iranian isolation and insecurity.

In recent months, unsettling rhetoric from senior Iranian individuals over the country’s nuclear programme – alongside continued Iranian advancements in this area and escalating tensions in the Middle East – has highlighted the urgency of finding a resolution to the now decades-old Iranian nuclear question. The options available to the US and its partners for inducing a roll-back of Iran’s programme are limited, given that economic threats and incentives, as well as security assurances, will be difficult to make meaningful and credible. However, Iran still appears to perceive some benefit from maintaining a threshold nuclear programme rather than developing a nuclear weapons capability. The US and its partners should leverage remaining carrots and sticks to reinforce this assumption, making clear to Tehran that it would be worse off with a nuclear weapons capability than its current threshold nuclear status.

Limited Incentives and Assurances

As it stands, US intelligence does not believe that Iran is conducting weaponisation-related research. However, the country possesses a highly advanced – and advancing – nuclear programme. The escalation in regional violence in the Middle East – including direct Iranian and Israeli strikes on each other’s territories – appears to have increased Iranian reliance on the advanced programme as a source of deterrence. In recent months, a number of senior Iranian individuals have alluded to the country’s technical and political ability to reconsider its stated policy of not pursuing nuclear weapons, should the need arise. Meanwhile, according to a recent poll, the Iranian public appears to be increasingly in favour of developing a nuclear weapons capability. Masoud Pezeshkian – the reformist candidate who secured the greatest number of votes in the first round of Iran’s presidential elections – has signalled a willingness to return to nuclear diplomacy. This is a positive sign; however, it is unclear how Pezeshkian’s intentions will align with the priorities of the Supreme Leader, who ultimately sets the direction of Iran’s foreign and security policy. Should hardliner candidate Saeed Jalili be elected to the presidency, a more conciliatory stance on the nuclear question would be unlikely.

There is increasingly a dearth of credible incentives and assurances that the US and its partners can offer Iran. One often-mentioned source of leverage is the option of ‘snapping back’ UN Security Council (UNSC) sanctions on Iran which had been lifted in 2016 under the Joint Comprehensive Plan of Action (JCPOA). If not snapped back, the suspended sanctions resolutions will expire in October 2025, removing the option of reimposing them and closing the Iran nuclear file at the UNSC. The prospect of passing new sanctions is highly unlikely considering the current politics of the UNSC. Snapback would reintroduce a range of international prohibitions and other restrictions on Iranian economic activity, including an expectation for member states to stop and inspect Iranian vessels suspected of sanctions violations and to ‘exercise vigilance’ when dealing with Iranian banks. Critically, it seems that snapback would likely result in the reimposition of targeted financial sanctions (TFS) on individual entities. Presumably, this would once again grant the Financial Action Task Force (the global financial crime compliance watchdog) a mandate to evaluate and report on member state compliance with said TFS, which it lost in October 2023.

While Tehran may have in the past felt that it could use its nuclear programme to secure concessions from the West, it has probably lost much of its value as a meaningful source of leverage for Iran

However, UNSC sanctions have lost much of their teeth in light of the increased politicisation of the UNSC and the expansion of Iran’s economic and military relationship with Russia. Furthermore, the expansive scope of US unilateral sanctions on Iran significantly limits the practical impact of UNSC sanctions reimposition, as many financial institutions globally already refuse to do business with Iran so as not to run afoul of US regulations. Any promises of US sanctions relief will also be challenging to make credible, regardless of who ends up in the White House following the election later this year. As became clear during efforts to revive the JCPOA in the first two years of the Biden presidency, the extent and complexity of US sanctions on Iran, as well as the massive political divide in Washington over how best to deal with Iran, mean that sanctions relief will be difficult to deliver even if Donald Trump does not return to the presidency. There is equally no guarantee that any diplomatic or economic promises would survive the 2028 presidential election. Europe’s impotence in offering Iran economic benefits after the reimposition of US sanctions in 2018 also undermines the credibility of any European offers of economic engagement with Iran. The negative normative implications of being a UNSC-sanctioned country are also likely to be of decreasing relevance to Iran as the practical economic impacts wane and as Iran continues to expand its political, economic and security relationships with Russia and others.

As such, while Tehran may have in the past felt that it could use its nuclear programme to secure concessions from the US, Europe and others, the programme has probably lost much of its value as a meaningful source of economic and diplomatic leverage for Iran. The primary value for Iran of an advanced nuclear programme now likely rests in a perception of its ability to deter – or secure assurances against – direct threats to Iranian security, namely the targeting of Iranian assets abroad, military attacks on Iranian territory, and regime change. Arguably, the programme has been unsuccessful in deterring against the first and – in part – the second. Israel has continued to target Iranian assets abroad and carried out a strike – albeit a limited one – on Iranian territory in April. However, Iran may still perceive some value in the programme’s ability to deter large-scale attacks on its territory or efforts at regime change. Incentivising Iran to roll back its nuclear programme would therefore require decreasing Iran’s reliance on its nuclear threshold status as a source of security. Tehran would need to be convinced that it would not become vulnerable to military strikes against its territory or forced regime change should it agree to nuclear concessions. Here, too, making credible commitments will prove challenging.

The US has in the past publicly stated that it is not pursuing regime change in Iran, and has reportedly privately communicated that message to Tehran more recently. The high political costs and escalatory risks of a US decision to carry out military strikes against Iranian territory – or even (perhaps to a lesser degree) US support to Israel or others for carrying out such strikes – should also provide Iran with some reassurance that it is highly unlikely that the US would pursue such a course of action. However, it is unclear to what extent the government in Tehran believes that the US would not accept these risks at some point in the future, particularly if Iran were to give up or significantly roll back parts of its nuclear programme.

Critically, the US cannot provide Tehran with credible assurances that Israel would not strike Iran. Washington can privately urge Israel against such attacks or refuse to materially support them (which may operationally undermine Israel’s ability to carry out certain types of attacks), but this may not be sufficient to forestall an Israeli decision to strike. Any commitments made in private could be easily denied and reneged on; meanwhile, public Israeli commitments not to strike Iran are politically unfeasible. The recent escalation in Iran’s nuclear rhetoric suggests that Tehran is not entirely convinced of US or Israeli restraint and still feels the need to flex its threshold nuclear status, presumably as an insurance policy against any such attacks.

Remaining Carrots and Sticks

Yet, weaponisation of the Iranian nuclear programme is not inevitable. The earlier-mentioned rhetoric from senior Iranian figures suggests that Tehran perceives its current threshold status as a sufficient guarantor of security. The relatively modest Iranian response to the recent Board of Governors resolution calling out Iranian unwillingness to cooperate with the IAEA also suggests that Tehran is for the time being unwilling – or does not see the need – to push the nuclear envelope much further than it already has. Recent reports of indirect diplomacy between Iran and the US through Oman, which seems to have succeeded in limiting progress on at least some parts of the Iranian nuclear programme, are also promising. There is, of course, no guarantee that this will hold perpetually. Should Iran feel that its threshold nuclear status is insufficient to guarantee its security – for instance, following further attacks on its territory or a further degradation of its regional assets and proxies – it could still decide to pursue a nuclear deterrent. A number of carrots and sticks remain available to the US and its partners to reinforce the message that Tehran stands more to lose than to gain from a decision to acquire nuclear weapons.

Despite the limited practical economic implications of reimposed UNSC sanctions, it is still worth threatening the possibility of snapback while it is still available; however, this should not be the sole point of leverage. The threat may produce little result, or it could convince Iran to make some limited concessions – perhaps increasing IAEA access to its nuclear programme or freezing enrichment levels. At the same time, 15 months is not a long time to resolve the myriad issues that would need to be addressed to justify the closing of the Iran nuclear file at the UNSC; Iran may just run down the clock by making perfunctory concessions that could be reversed after October 2025. Meanwhile, actually acting on the threat to reimpose sanctions would run a high risk of Iranian escalation – including a potential withdrawal from the Nuclear Non-Proliferation Treaty, which could make monitoring and preventing weaponisation harder. This catch-22 situation points to the ultimately limited relevance of snapback for meaningfully dealing with the Iranian nuclear question. Alternative options for incentivising and deterring Iran are needed.

The recent escalation in Iran’s nuclear rhetoric suggests that Tehran is not entirely convinced of US or Israeli restraint and still feels the need to flex its threshold nuclear status

Diplomatic and economic pressure from countries still friendly towards Iran may prove helpful. The acquisition of a nuclear weapon would likely lead to political and economic ostracisation by countries like China, India, South Africa and others that may tolerate a threshold Iranian nuclear capability but not a nuclear-armed Iran. Pre-emptively encouraging these countries to place additional pressure on Tehran to forego weaponisation – particularly in ways that threaten key diplomatic and economic lifelines for Iran – may help influence Iranian decision-making. However, the extent of influence that these countries would have in Tehran, and whether they would be willing to expend any political capital to prevent weaponisation, is debatable. Should the decision be made to snap back UNSC sanctions, this may grant the necessary political cover to increase economic and diplomatic pressure on Tehran for countries that wish to do so.

Maintaining diplomatic channels between the US and Iran – even indirect ones like the Omani channel mentioned above – will remain important for making it clear to Tehran that a diplomatic resolution remains possible. At the same time, sensitively communicated threats of military escalation by the US should not be ruled out. Making any such threats credible will be challenging, however. The advanced and hardened state of Iran’s nuclear programme will make it impossible to permanently eliminate the possibility of it being reconstituted in the future. Meanwhile, risks of escalation in regional violence and political pushback even from allies would be very high. Washington may in the end decide that the gamble is not worth the uncertain prize. However, the escalatory risks should also mean that strikes would not be considered short of the most extreme of circumstances – namely, an Iranian decision to weaponise. Drawing red lines in this instance would also be challenging, as defining and detecting a decision to weaponise will be difficult. However, this ambiguity could be helpful in discouraging Iran from trying to test how much it can get away with. Any military threats must be made discreetly, denying Iran the opportunity to point to such threats as a reason for future escalation of its nuclear programme. Such discretion will also allow Tehran to save face by avoiding the perception that it is making concessions to Washington, while equally permitting the US to retain flexibility in deciding whether and when Iran has crossed a red line.

The proposed solutions are imperfect – none guarantee success, none will be straightforward to implement and some – particularly threats of UNSC sanctions snapback or of military attack – pose the risk of backfiring. The US and its partners will need to weigh these and other policy options against assessments of how likely Iran is to be moving towards a decision to weaponise its programme, and how much convincing is needed to keep it from doing so. Hard decisions may have to be made on whether certain risks may ultimately be necessary and worth taking to avoid the potential emergence of a nuclear-armed Iran.

The views expressed in this Commentary are the author’s, and do not represent those of RUSI or any other institution.

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