Clinton said the Bush administration would be wrong to assume it could attack Iran based on the 2001 Congress resolution allowing force against those responsible for the September 11 attacks and a 2002 vote authorising war against Iraq.

The 2008 Democratic presidential hopeful voted in favour of the Iraq war in 2002, a vote that she has refused to say was a mistake despite calls by anti-war Democrats for her to recant it.

"It would be a mistake of historical proportion if the administration thought that the 2002 resolution authorising force against Iraq was a blank check for the use of force against Iran without further congressional authorization," Clinton said in the Senate.

"Nor should the president think that the 2001 resolution authorising force after the terrorist attacks of 9/11 in any way authorises force against Iran," she said.

"If the administration believes that any, any use of force against Iran is necessary, the president must come to Congress to seek that authority," she said.

Her comments came as Bush said an elite force of Iran's Revolutionary Guards was the source of powerful new bombs used by insurgents against US soldiers in Iraq, although he said he was unsure whether Iran's leaders were behind the shipments of arms.

The allegations of Iranian bombs in Iraq and Washington's dispute with Tehran over its controversial nuclear programme have raised concerns of a possible war.

But Bush said Wednesday there was "good progress" toward solving the nuclear dispute "peacefully."

On Monday, he dismissed talk of a likely US attack on Iran as "noise" from his critics.

Western powers fear Iran would use its nuclear technology to build a nuclear bomb, but Tehran insists its programme is solely to meet its energy needs.

A dozen lawmakers in the House of Representatives, including Democrats and members of Bush's Republican party, introduced legislation last month barring the White House from attacking Iran without Congress's green light.