Generally, those who argue against a military strike stop 10 yards short of the finish line. After concluding that a strike would not make sense, they still tend to tolerate leaving it as a last resort. There are dangers to such an approach. Mr Obama may some day come under pressure to employ it when all else has failed – and we think this would be a mistake, not only for the specific matter of Iran policy but more broadly for his effort to recast the US as a country playing by international legal norms.

In addition, keeping the option of force requires US diplomats and military officials to take preparatory steps that may distract from our current efforts in Iraq and Afghanistan, and complicate a number of regional bilateral alliances. Some states in the Middle East, such as Saudi Arabia and the United Arab Emirates, are generally worried about Iran. But few are anxious to support moves towards war. We will be better positioned for a sustained tightening of regional alliances if we remain resolute yet fundamentally defensive in our orientation and strategy.

There is a better way: sanctions, deterrence and containment. To be sure, another nuclear-armed state in the Middle East, especially one touting the extremist views of the current Iranian regime, would be bad for regional security. But Iran would be suicidal to attack a US ally in the region – especially one such as Israel, which has a formidable nuclear arsenal by all accounts. Iran has already proved its willingness to wage proxy and terror wars against the US and Israel. It is doubtful that a small nuclear arsenal would offer it many more options than it has already.