President Bush said today that he still believes Iran poses a danger to the world despite a stunning new assessment from US intelligence agencies that Tehran halted its weapons programme as far back as 2003 and has not restarted it.

Describing the latest National Intelligence Estimate, released yesterday, as a "warning signal" that the Iran could restart a covert weapons programme, Mr Bush insisted military action would remain an option.

Though he accepted Iran had ended its weapons programme for now, it was still trying to learn how to enrich uranium, he noted, "an important step in a country whose desire it was to develop a nuclear weapon."

"The thing that would make a restarted programme effective and dangerous is the ability to enrich uranium," he said.

The report, reflecting the consensus view of all 16 US spy agencies, contradicted earlier reports from the same body and appeared to undercut Mr Bush's repeated warnings about Iran becoming a nuclear power.

But Mr Bush insisted the report had in fact vindicated his approach to the crisis, having shown the sanctions and pressure applied by the United States to be effective.

“To me, the NIE (National Intelligence Estimate) provides an opportunity for us to rally the international community - to continue to rally the community - to pressure the Iranian regime to suspend its programme."

He rejected suggestions that following erroneous intelligence on Iraqi WMD, the United States would now be viewed as "the boy who cried wolf," saying only that "nothing's changed." Neither would he address the discrepancy between the latest assessment and his earlier rhetoric, including an assertion last month that a nuclear Iran would lead to "World War Three".

“I think the NIE makes it clear that Iran needs to be taken seriously as a threat to peace. My opinion hasn’t changed."

Predictably enough, the report was welcomed in Iran, where a foreign ministry spokesman said that it showed Mr Bush's statements to be "unreliable and fictitious".

But in Britain, Gordon Brown's spokesman said that the potential threat from Iran's nuclear programme remained a very serious issue.

“We do need to examine the details of this report,” he said. “But in overall terms the Government believes that the report confirms we were right to be worried about Iran seeking to develop nuclear weapons.

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