The US maintains that Iraq is being obstructive

Chief weapons inspector Hans Blix told the UN Security Council that international pressure had forced Iraq to accelerate its co-operation with the teams searching for weapons of mass destruction, and that their work could be completed within months.

But Britain, a key US ally, has suggested amending a proposed Security Council resolution to give Iraq a deadline of a few days - until 17 March - to show "full, unconditional, immediate and active" co-operation with inspectors.

The new resolution, likely to be introduced next week, is intended to win the support of at least nine Security Council votes - including France, Russia and China, all of which have the power of veto over such a resolution and have expressed serious reservations about the prospect of war.

The destruction [of missiles] undertaken constitutes a substantial measure of disarmament... We are not watching the breaking of toothpicks, lethal weapons are being destroyed Hans Blix Chief UN weapons inspector Read the key points of the report

Announcing the move, British Foreign Secretary Jack Straw said: "It defies experience that to continue inspections with no firm end date... will achieve complete disarmament."

He was backed by US Secretary of State Colin Powell, who maintained that Iraq's disarmament efforts had not amounted to the voluntary, active co-operation demanded by UN resolutions.

Referring to the massive build-up of US and British forces in the Gulf region, he said: "Nobody wants war but it is clear that the limited progress we have seen comes from the presence of a large military force.

"It comes from the unified political will of this council and the willingness to use force - if it comes to that - to make sure that we achieve the disarmament of Iraq.

"Now is the time for the council to tell [Iraqi President] Saddam [Hussein] that the clock has not been stopped by his stratagems and his machinations."

French Foreign Minister Dominique de Villepin said Iraq was less of a threat to the world than it was before the 1991 Gulf War.

"We cannot accept an ultimatum as long as inspectors are reporting co-operation," he said.

"France will not allow a resolution to pass which would authorise the automatic use of force."

Russia and China also expressed doubts about a resolution backing military action.

'Not authentic'

In his report, Mr Blix said inspectors had been able to conduct operations throughout Iraq with relative ease and described the ongoing destruction of al-Samoud II missiles as a "substantial measure of disarmament".

HOW THE UN MIGHT VOTE Country-by-country voting intentions

However, he added that such co-operation could not be described as "immediate compliance" - as required by resolution 1441, passed late last year by the Security Council.

He also said there was no evidence to support US claims that Iraq was hiding biological and chemical weapons in mobile laboratories and underground shelters.

But he added that Iraq had failed to provide sufficient documentary information about weapons it claimed to have destroyed, and that interviews with Iraqi scientists appeared to have been subject to "outside pressure".

In his report, the head of the International Atomic Energy Agency, Mohammed ElBaradei, said there was no evidence that Iraq had restarted the nuclear weapons programme it was forced to abandon after the Gulf War.

He challenged US and UK allegations on two key issues.

Reports that Iraq had tried to purchase uranium from Niger were based on documents that were "not authentic", he said, while extensive examination of imported aluminium tubes suggested that they were not destined for use in enriching uranium.

Mr ElBaradei added that there had been progress on interviewing scientists without minders or tape recorders, but implied that there was still concern that interviews were being bugged.

On the eve of the report, US President George W Bush emphatically set out his agenda for the discussions.

He said the US would call for a new UN vote to pave the way for military action, whatever the level of support in the Security Council - but warned that the US was in the final stages of diplomacy.

In other developments:

• UN observers say they have found three large gaps in the fence on the Iraq-Kuwait border which may be used in a military advance against Iraq

• Britain's most senior soldier, General Sir Mike Jackson, says his troops are ready to move immediately if the order comes to invade Iraq

• Experts on international law say war against Iraq could be "illegal".