As recently as a year ago it was the strong conviction of many Washington insiders that a decision by the Bush Administration to attack Iran’s nuclear facilities was not a matter of if but when.

Yesterday’s National Intelligence Estimate, which concluded that Iran halted its nuclear weapons programme back in 2003, probably spells the end of the threat of a new confrontation by the United States.

The Administration’s dwindling number of hawks, led by the Vice-President, Dick Cheney, had been trying to keep the pressure up for possible action, insisting that a decision to use force was “still on the table” because of Iran’s failure to cooperate with the International Atomic Energy Agency. US naval forces have been conducting exercises in the Gulf and the Pentagon has leaked plans for an air assault against Iran’s key installations, notably the Natanz facility, where Iranian nuclear physicists are enriching uranium.

But an attack would be hugely risky and probably self-defeating. There is no guarantee that air strikes could disable Iran’s nuclear programme. There is every chance that Iran would retaliate against US forces in Iraq, use its Hezbollah proxies in Lebanon to attack Israel and wage a global terrorist campaign against US targets.

Above all Washington would need domestic and international support for any military campaign. That seems impossible to achieve while US intelligence agencies do not consider Iran to be a threat.

The conclusion will be greeted with relief in the West, particularly Britain, which still has a sizeable force based in southern Iraq and naval forces in the Gulf, which could have been drawn into any US-Iranian confrontation.

While US intelligence may not regard Iran’s nuclear programme as an immediate threat, that does not mean other nations in the region will be mollified. The Arab Gulf states, which are embarking on their own nuclear programme, regard a resurgent Iran, with or without nuclear weapons, as the greatest threat to regional stability.

Above all, Israel remains very concerned about the threat posed by Iran, whose leader, President Mahmoud Ahmadinejad, once suggested the Jewish state should be “wiped off the map”.

If American military action against Iran is today less likely than before, then there is a greater chance that Israel may take unilateral action for what it would regard as an act of self-defence.

Times Recommends

• Rio Tinto four held as China prepares case
• Diplomats must keep heads down and trousers up
• When in Rome should one make like Berlusconi?