Few believe that the ongoing nuclear talks between the US and Iran will succeed. The two parties are far apart diplomatically, and Tehran’s increased demands and technical nuclear advances of late have made a return to the 2015 Joint Comprehensive Plan of Action unlikely. Should the current nuclear standoff persist, what should Washington do? Like his predecessors, US President Joe Biden is committed to stopping Tehran from acquiring nuclear weapons. But his administration has not clarified what its official position is regarding a nuclear-threshold Iran – that is, an Iran that has the capability to quickly build an atomic weapon but doesn’t actually do so. While it is unknown whether Iran is already a latent nuclear state, it is certain that the country is closer than ever to becoming one. This creates a serious dilemma for Washington. On the one hand, an Iranian bomb, especially if kept in the basement, does not constitute a direct threat to the US. On the other, if Washington does not stop Iran from achieving nuclear latency, the Israelis could likely launch an attack against Iran because they would view such an outcome as an existential threat. Israel’s concerns of any kind of advanced Iranian nuclear capability, latent or operational, are deeper than those of any country in the region, considering the tragic Jewish experience during the Second World War. The position of the Israelis no doubt complicates and adds a sense of urgency to US policy. They much prefer not to use force against Iran without Washington’s diplomatic and military support, but they could if they have to. They did it before, both in 1981 against Iraq’s Osirak nuclear research reactor and in 2007 against Syria’s Al Kibar nuclear facility. Granted, Iran’s nuclear infrastructure is a lot more extensive and dispersed. Also, the Iranians have spent many years investing in stronger defences, precisely to prevent the Iraqi and Syrian scenarios. And unlike the Iraqis and the Syrians, the Iranians have serious retaliatory options, be it directly with their considerable missile force or through their well-armed proxies in the region, including Hezbollah and Hamas. An Israeli-Iranian kinetic exchange could easily lead to a regional war. The Israelis are fully aware of the limitations and potentially immense costs of any airstrikes they might launch against Iran. They know they don’t have the capability to destroy Iran’s nuclear programme in its entirety. They also expect that Iran will rebuild, possibly in a short time, everything Israeli jets will destroy. But this is unlikely to deter them because they believe nothing threatens their survival more than a regime that does not accept their existence and can either use a nuclear weapon against them or extend a nuclear umbrella to its regional allies. To avoid a regional war, the Biden administration must communicate very clearly to the Iranians that it cannot tolerate nuclear latency. If the Iranians ignore US wishes and continue to enrich uranium at higher levels, Washington will have three not-mutually-exclusive options to consider to increase the pressure against Tehran: more economic sanctions, clandestine operations and overt military force. Of these three, the credible threat of military force is most likely to push Tehran to reconsider its maximalist negotiations tactic. Iran has survived harsh US and international sanctions for years, and further economic punishment will most probably not change its behaviour, especially if China continues to buy Iranian oil at a discounted price. The same logic applies to cyber-attacks or assassinations of Iranian nuclear scientists – tools that have allegedly been used by the US and Israel but to no avail. Yet the conventional military option is one Washington is least eager to entertain, let alone use. Mr Biden came into office determined, like his two predecessors, to focus on domestic policy and strategic competition with China, primarily in East Asia. The last thing he will agree to is launch another costly US military intervention in the Middle East. But the US could find itself dragged into a regional war anyway if Tehran keeps pursuing nuclear blackmail and Israel responds militarily. The use of force against Iran should never be taken lightly, especially after the US strategic disaster in Iraq. The risks are not small and the payoffs are not clear. But it is thoroughly misguided and downright disingenuous to compare a surgical strike against Iranian nuclear facilities to what the US did in Iraq in 2003. No one could rightly argue for toppling the Iranian regime like the US did in Baghdad. The goal here is to push Iran to adjust its nuclear calculus and make the necessary concessions. Most American critics of the use of force against Tehran believe, some openly, that the world can live with a nuclear-armed Iran. They argue that the US has dealt with nuclear-armed adversaries such as Russia, China and North Korea, and Iran should be no different. Except that Iran is, in fact, very different. None of those countries has a leadership that is guided by religious ideology. Also, Iran has caused more bloodshed and sown more chaos in the Middle East than any of these three countries in their respective regions. Now imagine a radical Iran bent on regional hegemony and armed with the absolute weapon: it is a recipe for not only regional war but also nuclear proliferation. It is a stretch to believe that such costs are more tolerable than Washington’s use of precise military force against Iran’s nuclear facilities. It is true that there is no military solution to the nuclear crisis with Iran. But to suggest that Iran will not be deterred under pressure, or that any use of force against it is unacceptable or morally objectionable, is flat out wrong. Negotiations must be the only pathway to a resolution of this crisis, but to save diplomacy and avert war, Washington has to clearly communicate its red lines to Iran and credibly threaten to use force if Iran ignores them.