Nato was plunged into crisis last night as the stand-off over Iraq laid bare deep divisions at the heart of the Western alliance.

France and Germany - the leading opponents of conflict with Iraq - combined to block moves to send Patriot missiles and other Nato hardware to defend Turkey in the event of a war.

US Defence Secretary Donald Rumsfeld described the Franco-German position as "shameful" while Nato Secretary General Lord Robertson warned of "serious implications" for the alliance if the differences could not be overcome.

'The longer this dispute goes on, the worse it is going to be for the alliance," he warned.

Downing Street sought to play down the row, insisting that discussions over providing assistance to the Turks were still continuing.

Greece, which holds the rotating presidency of the European Union, said that it wanted to call an emergency EU summit to try to heal the "crisis" in trans-Atlantic relations. However it was unclear whether it would actually go ahead.

Certainly, there was no disguising the fury of the Americans who have been pressing for Nato to allow contingency planning to begin to defend Turkey in the event of a conflict.

The US was already angry at a leaked Franco-German plan - supported by the Russians - to massively increase the number of UN weapons inspectors in a final attempt to head off a war.

It led to angry exchanges involving Mr Rumsfeld at a conference in Munich at the weekend.

Last night, France and Germany turned the screw further with a little help from Russia.

The three countries issued a joint declaration calling for strengthened UN weapons inspections in Iraq, part of a diplomatic initiative aimed at disarming Saddam Hussein without war.

French President Jacques Chirac, reading the declaration in the presence of visiting Russian President Vladimir Putin, said Iraq's weapons capability must be neutralised as quickly as possible - but that waging war to achieve the objective should only be considered as a last resort.

At the same time, Iraq said it would agree to the use of American U-2 spy planes by weapons inspectors over its territory and pledged to pass legislation next week outlawing the use of weapons of mass destruction.

In an interview with the Italy's La Republica newspaper, Mr Rumsfeld complained bitterly at the opposition of the French and Germans - backed by Belgium - to allowing Nato planning to defend Turkey.

"Shameful, for me it's truly shameful. Turkey is an ally. An ally that is risking everything. How can you refuse it help?" he said.

He later told reporters that planning to protect Turkey would go ahead "outside of Nato if necessary".