Prime Minister Tony Blair's official spokesman said Britain remained ready to use force if a diplomatic solution could not be found.

"If the use of force is necessary that is the course that will be taken," he said.

Defence Secretary George Robertson has already warned President Hussein to stop obstructing UN weapons inspections or "face the consequences".

Mr Robertson said Iraq had "no choice" but to comply with Security Council resolutions which require him to let monitors search for chemical weapons.

He said: "All the options would be considered very carefully before anything was done to Iraq, but what Iraq must understand is it has no choice in this matter, it must comply with the UN Security Council regulations or face the consequences."

Baghdad suspends co-operation

Iraq halted co-operation with UN arms inspectors on Saturday and demanded a lifting of the eight-year UN embargo - imposed after the 1990 invasion of Kuwait.

Iraq wants inspection head Richard Butler removed

It also demanded the dismissal of the top weapons inspector, Richard Butler, and a restructuring of Unscom, the UN inspection body.

A Foreign Office spokesman said the move was "totally unacceptable".

"Iraq is again flouting the Security Council resolutions and the memorandum of understanding it signed with the UN secretary general."

Shadow Foreign Secretary Michael Howard said the Iraqi move was "a very serious development".

"When Iraq refused to co-operate with these inspectors earlier in the year, [Foreign Secretary] Robin Cook was full of tough talk.

"He should make an early statement of government intentions in the face of this serious news."

UN in the dark

Until now the inspectors who were on the trail of Iraqi missiles and chemical weapons had been forbidden by Iraq to do their work.

But the complex job of monitoring those sites which were previously inspected was allowed to continue.

That has now stopped and the UN will effectively have no eyes or ears in Baghdad.

Iraq added that it would not interfere with inspectors checking nuclear installations.

Emergency meeting

The new move follows a decision on Friday by the UN Security Council to review Baghdad's compliance with UN resolutions on weapons of mass destruction - but without any guarantee that this would lead to a lifting of sanctions against Iraq.

Iraq's leadership justified its latest action by saying it had conformed to Security Council's resolutions "in the hope that the unjust embargo imposed on its people would be lifted".

The Security Council is holding an emergency meeting on Saturday to discuss Iraq's move.

US reaction cautious

The sanctions, imposed after Iraq's 1990 invasion of Kuwait, cannot be lifted until the UN Special Commission certifies that Iraq has eliminated its biological and chemical weapons and long-range missiles.

France also said it "deplored" Iraq's move.

A government spokeswoman said: "France urgently calls on Iraq to resume full and complete co-operation with the UN."

Reaction so far from the US has been cautious.

The BBC correspondent in Baghdad, Richard Downes, said: "The Iraqi reasoning is clear.

"They believe that there is no international appetite for a new confrontation and they think that countries inside and outside the (UN) alliance are much more sympathetic to their cause."