Meanwhile, what about Iran?

''The question people are going to ask," said Tony Blair, "is, 'What are you going to do about Iran?' Because - can you imagine a state with an attitude like that having nuclear weapons?" The Prime Minister responded to the Iranian president's threat to wipe out Israel with a question of potentially momentous significance. The precedent of a "rogue state" alleged to be working on weapons of mass destruction is alarming, but do experts think an attack on Iran is possible?

According to Francis Tusa, editor of Defence Analysis magazine, it would be a mistake to think the US can not, on its own, muster the manpower needed - it might be difficult but "there are naval and air forces of sufficient quantity and quality". He would, however, be "gobsmacked" if such an attack happened: after Iraq, Washington has learned that such actions demand broad alliances. "The unilateral way is not the way to go."

At the International Institute for Strategic Studies, Patrick Cronin agrees: "There is a military option because Washington refuses to take it off the table." But he adds: "It is not pursuing military options right now."

Both agree that President Ahmadinejad's words were so inflammatory the international community could not let them pass. In Cronin's words, it was a watershed; he foresees a worrying escalation, with the issue jumping from the realm of diplomacy to the UN Security Council, where public exchanges and the role of the hardline US ambassador John Bolton could soon push matters to sanctions and ostracism.

Tusa points out that, while Iran might appear to be courting confrontation - developing its nuclear capacity, allegedly helping insurgents in Iraq and stirring hatred against Israel - "there is a danger of putting everything in one conspiracy theory". It is not clear, for example, whether involvement in Iraq is directed from Tehran or comes from local groups and branches of the Revolutionary Guard. That said, he believes the next big decision lies with Tehran: will it take the nuclear programme to the next phase? That, and not outbursts about Israel, will be the real test.