The secret report, which was declassified on Monday and published, marked a significant shift from previous estimates. “Tehran’s decision to halt its nuclear weapons programme suggests it is less determined to develop nuclear weapons than we have been judging since 2005,” it said.

The disclosure makes it harder for President George Bush to justify a military strike against Iran before he leaves office next year. It also makes it more difficult to persuade Russia and China to join the US, Britain and France in imposing a new round of sanctions on Tehran.

Bush and Vice-President Dick Cheney have been claiming that Tehran is bent on achieving a nuclear weapon, with the president warning in October of the risk of a third world war. They were briefed on the national intelligence estimate (NIE) on Wednesday.

White House national security adviser, Stephen Hadley, at a press conference on Monday, denied there were echoes of the intelligence failure over Iraq’s phantom weapons of mass destruction. He said that Iran was “one of a handful of the hardest intelligence targets going” and the new intelligence had only arrived in the past few months. As soon as it did, both the president and Congress had been briefed. He warned that there would be a tendency now to think “the problem is less bad than we thought, let’s relax. Our view is that would be a mistake.”

The NIE, which pulls together the work of the 16 American intelligence agencies, is entitled Iran: Nuclear Intentions and Capabilities. It concluded: “We judge with high confidence that in fall 2003 Tehran halted its nuclear weapons programme.” It had not been restarted as of the middle of this year.

In a startling admission from an administration that regularly portrays Iran as the biggest threat to the Middle East, the NIE said: “We do not know whether (Iran) intends to develop nuclear weapons.” That contradicts the assessment two years ago that stated that Tehran was “determined to develop nuclear weapons”.

Still a danger, says Bush
Washington, Ruters: President George W Bush said on Tuesday that Iran remains a danger despite a US intelligence report that Tehran halted its atomic weapons programme four years ago.

Bush also said “all options” are on the table for dealing with Iran. He was speaking at a news conference a day after intelligence agencies released the assessment on Iran.