The United Nations chief weapons inspector Hans Blix last night applied the brakes on America's drive to war with Iraq, insisting that Saddam Hussein could still be disarmed without the use of force.

Foreign Secretary Jack Straw and US Secretary of State Colin Powell warned the UN Security Council that there must be no backing away from the threat of military intervention.

However, Tony Blair and President George Bush faced powerful opposition from France which said that Dr Blix's report showed that inspections were working and should be given more time.

In an impassioned speech - which won a rare round of applause - French Foreign Minister Dominic de Villepin insisted that war was not justified at the present time.

With Russia and China - the other two permanent members of the Security Council - also calling for more time for inspections, Britain and the US appeared to have little chance of gaining a new UN resolution authorising force.

The governments in Washington and London will have to consider carefully their next step over the coming days as they decide how long to continue with the diplomatic process.

Although Dr Blix said Iraq still had not accounted for large quantities of biological and chemical agents used to produce anthrax and VX gas, his second report to the Security Council was much more of a mixed bag than his first one two weeks ago.

He said that Iraq was beginning to hand over documents, had allowed its scientists to talk to the inspectors without a minder present, and had agreed to surveillance flights by U2 spyplanes.

Dr Blix also challenged satellite evidence presented to the Security Council by Mr Powell that the Iraqis had "cleaned up" its chemical sites before the inspectors, saying that it may only have shown "routine movements".

With the "immediate, active and unconditional" co-operation of the Baghdad regime, the disarmament of Iraq through inspections could still be achieved in a "short" period of time.

Mr Straw said it was clear that Iraq remained in "material breach" of its obligations to disarm and said that it must end its defiance or face "serious consequences".

"I hope and believe that a peaceful solution to this crisis may still be possible, but this will require a dramatic and immediate change by Saddam and this will only be achieved if we, the Security Council, hold our nerve in the face of this tyrant," he said.

Mr Powell said that in the "very near future" the Security Council would have to discuss whether it had reached the point to consider the use of military force.

Last night, Liberal Democrat leader Charles Kennedy said it would be "inconceivable" for the UK to back military action in Iraq without the authority of the UN. "At this stage, there is no just or moral case for war," he said.

Labour's Tam Dalyell, Father of the House of Commons, said it would be "wicked, wicked, wicked" to go to war on the basis of the inspectors' reports.

Mr Dalyell said: "There is not a shred of an excuse for launching a military attack on the basis of this report. Not a shred."

But Tory leader Iain Duncan Smith said pressure had to be increased on Iraq. "Hans Blix said today that unless Saddam Hussein co-operates - and he has not done - then he cannot complete that task of destroying those weapons of mass destruction."