Nobody, the Bush Administration included, really wants the United States to attack Iran. So everybody will drag their feet as much as possible. There may be 12 more months of diplomatic manoeuvring before the crisis hits.

But there is going to be a crisis, and it is going to be big and dangerous.

Work at the Isfahan uranium conversion plant - suspended temporarily last November - has resumed. At the same time Iran has rejected the last offer of the "EU-3" (Britain, France and Germany) - a package of economic inducements designed to persuade it to abandon its nuclear ambitions.

Iran's top nuclear negotiator, Hassan Rohani, is leaving his job to make room for somebody more congenial to the new, hardline President, Mahmoud Ahmadinejad, and Iran is calling the Europeans' bluff. It may be calling the American bluff, too.

There is a significant possibility that President George W. Bush is bluffing when he hints that he might attack Iran if it doesn't halt its nuclear fuel programme.

He doesn't actually say he will, just that all options are on the table - and his options are not actually very good.

It's clear that the Bush Administration, already up to its neck militarily in Iraq, is reluctant to get into a war with Iran, and the best evidence for that is the recent US National Intelligence Estimate (NIE), which that Iran is 10 years away from developing nuclear weapons. Six months ago it said five years.

The US intelligence agencies generally offer a range of possible conclusions, given the diversity and unreliability of intelligence sources. The administration that provides the agencies' budgets can usually manipulate the process to highlight the conclusions that it prefers (as in the invasion of Iraq).

The fact that the NIE now says 10 years, while Mossad, the Israeli intelligence agency, says three years, is a fairly reliable indication of the relative enthusiasm in the US and the Israeli Governments for an attack on Iran.

Neither estimate need be true, of course. Iran insists that its civil nuclear power ambitions are not a cover for a nuclear weapons programme, and the fact that it has lots of oil does not prove that it is lying.

It can make good economic sense to export oil for a huge profit and generate your own electricity: nobody says that Mexico must not build nuclear power plants.

But the fact that Iran is seeking to develop a nuclear enrichment capacity that would make nuclear weapons possible is deeply suspicious, since it would be far cheaper to buy the enriched uranium abroad.