"The fact that Iraq is in possession of undeclared chemical warheads, which the United Nations says are in excellent condition, is troubling and serious," he said.

He added it had become "increasingly clear" that Iraq was not disarming.

In an interview with the German newspaper Sueddeutsche Zeitung, Mr Powell noted that many nations believed a new Security Council resolution was necessary to justify a war.

He said the US took these concerns seriously, "but we have always made clear that the UN will act without a second resolution, if we are of the firm opinion that Iraq still has weapons of mass destruction or wants to produce new ones."

Mr Blix said the warheads discovery was "evidently not very good," but said it was "not a very big quantity".

The warheads are being tested to determine if they ever contained banned chemicals - Baghdad says they are merely empty rockets that have expired.

Mr Blix has said he wants more explanations from the Iraqis about the warheads.

After the meetings in Europe, Mr Blix will fly to Baghdad for talks with his inspection team and Iraqi officials, before giving a preliminary report to the UN Security Council in New York on 27 January.

Iraqi defiance

Saddam Hussein marked the 12th anniversary of the start of the Gulf War on Friday with a defiant speech in which he warned that US-led forces faced certain death if they attacked Iraq.

America had been "defeated" the last time it waged war against Iraq, he said, and had proved itself incapable of learning from past mistakes.

Our correspondent in Baghdad says Saddam Hussein's speech had a clear message for the outside world: that he has no intention of leaving Iraq for exile, as some media reports have suggested.

Saddam Hussein made no reference to the 11 warheads found on Thursday at the Ukhaider military storage facility.