The resolution would have to be passed by the House and Senate and signed by George Bush, the US president, to acquire the force of law.

"No trust"

It would waive the congressional authorisation only if Iran attacked the US or its armed forces, or if such an attack was "demonstrably" imminent.

So far, Jones' resolution has 11 co-sponsors in the 435-member House.

At the White House, Bush, asked whether there were any US plans to take action against Iran, said: "I have made it clear that if they're moving weapons inside Iraq that will hurt the cause of democracy and more particularly hurt our soldiers, we'll take care of business there.

"We're not going to let them."

Martin Meehan, a Massachusetts Democrat, said that while he did not trust Iran or its intentions in the Middle East, he also did not trust the White House.

Meehan said the resolution on Iran was needed because the Bush administration had "lied so many times" in the run-up to the US invasion of Iraq in 2003.

Concerns about a US attack against Iran increased after the United States moved an additional aircraft carrier into the Gulf region and the Bush administration told Arab allies it would do more to contain Tehran.

The legislation's backers said they hoped Democratic leaders in the House would advance their resolution in coming months, possibly as part of Iraq war funding legislation or other Iraq-related measures.