German Foreign Minister Joschka Fischer has directly challenged the United States over the justifications for possible military action against Iraq.

More than 10,000 protesters took to the streets in Munich

"I am not convinced... I cannot go to the public and say these are the reasons because I don't believe in them," he told a European defence conference in Munich.

US Defence Secretary Donald Rumsfeld earlier appealed to America's allies to act urgently against world terrorism, as the UN chief inspectors returned to Iraq.

US officials reacted angrily to reports that Germany and France were formulating a new UN resolution, which they refused to discuss with the Americans.

An article in Der Spiegel news magazine, confirmed by German officials, said the plan envisaged deploying UN troops to Iraq to support extended weapons inspections.

It would also declare the whole of Iraq a no-fly zone, and tighten sanctions on exports to the country.

But when Mr Rumsfeld tackled his German counterpart Peter Struck about the proposal, he was told: "We're not ready to discuss it yet."

"The last thing you want to do is to lay on a major diplomatic proposal through the press," said a senior US official.

Need to act

Mr Rumsfeld told his European audience - including EU foreign policy chief Javier Solana and Nato Secretary General Lord Robertson - that Iraq had to be tackled or the cost could be "unthinkable".

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Where key nations stand on Iraq

He said he could not believe there were still doubts about Saddam after the presentation of intelligence data by Secretary of State Colin Powell to the UN Security Council last Wednesday.

"The threat is there to see and if the worst were to happen and if we had done nothing to stop it, not one of us here today could honestly say that it was a surprise," he said.

He said Saddam had crossed "17 lines in the sand" marked by UN resolutions and had to be stopped from continuing to defy the international community.

But Mr Fischer said he wanted the Security Council to be given more time to find a diplomatic solution.

At least 10,000 people rallied outside the conference venue in Munich to protest against any war in Iraq.

Turkey defence

Mr Rumsfeld also attacked European reluctance to provide security guarantees to Turkey, the only Nato member to border Iraq.

Rumsfeld: Iraq has flouted international rules

He had excoriated Nato allies Germany, France and Belgium for trying to stall the deployment of defence equipment to Ankara.

Those countries fear that defence planning for Turkey could undermine diplomatic efforts to avert an attack on Iraq.

Nato Secretary General Lord Robertson said at the security conference that there was "complete agreement" over the alliance's commitment to protect Turkey.

He said he was confident that a plan to send help to the country would be made soon.

Germany and the Netherlands will supply Patriot missiles to Turkey at the end of next week, according to the French news agency AFP.