The UK has set out six conditions that Iraq must fulfil to avoid war, calling for them to be attached to a new UN Security Council resolution.
It is now unclear whether British troops will go into action
The six new tests of disarmament include demands for Saddam Hussein to make a public statement admitting he has weapons of mass destruction (WMD) and for Baghdad to allow scientists to be questioned abroad before a set deadline.
Britain, the US and Spain are co-sponsoring a UN resolution which will pave the way for military action against Iraq, and are currently trying to win enough backing within the Security Council to see the motion passed.
But amid clear threats of a veto from permanent members of the Security Council such as France and Russia, Spain indicated on Wednesday that the resolution may never be tabled.
At a press conference later, the UK Foreign Secretary Jack Straw failed to quash speculation that the three allies were considering withdrawing the motion, refusing to guarantee that a resolution would be put to the council for a vote.
The new conditions set by Britain will form a "side document" to the proposed resolution, providing a way of interpreting what the text means, the Foreign Office says.
UK BENCHMARKS FOR IRAQ
30 scientists must be allowed to be interviewed abroad
Stocks of anthrax and other material must be identified
Al-Samoud missiles and their engines must be destroyed
Drones must be accounted for
Mobile bio-warfare laboratories must be surrendered
The extension of a 17 March deadline for Iraq to convince the world it is disarming - as set out in the draft resolution - is one issue still under discussion, reports say.
Mr Blair, who faces intense domestic opposition to war, has been hoping that a second resolution authorising war will convince the British public of his case.
But Washington appears to be growing increasingly frustrated with the diplomatic process.
"The president has given diplomacy a certain amount of time. He
will not give it forever," said White House spokesman Ari Fleischer on Wednesday.
On Tuesday the country's defence secretary Donald Rumsfeld controversially suggested the US could go to war without Britain.
London has sought to play down the remarks, and Mr Blair insisted on Wednesday that it was in the British national interest to take action against Iraq.
He said it was not a question of the US going it alone, but of supporting a UN policy of disarmament in Iraq.
In other developments:
- In Turkey, police clash with protesters opposed to the possible use of Turkish bases by American troops
- The UN orders its international staff out of the Kurdish-held area of northern Iraq - evacuation is expected to take place on Thursday
- Former US President Bill Clinton tells a convention that he believes war can be avoided if the US backs a British resolution
- The EU warns it might be unwilling to fund reconstruction of Iraq is the US goes to war without UN backing
- Russian Foreign Minister Igor Ivanov says a war in Iraq will complicate matters elsewhere
- Baghdad says a drone - which the US claims could be used to deliver chemical and biological agents - is only a prototype and flew only three kilometres (1.9 miles) on its test flight
The UK Government is under increasing pressure from members of the ruling Labour Party over its tough stance on Iraq.
Iraq denies claims that its drone can deliver chemical weapons
Following Mr Rumsfeld's remarks, many Labour members are expected to call on Mr Blair's government to withdraw British military involvement.
After the UK Government questioned the comments, Mr Rumsfeld issued a statement saying he believed London would make a significant contribution.
However the statement did not say UK troops would actually fight.
British Defence Secretary Geoff Hoon told the BBC on Wednesday that Mr Rumsfeld had been referring to a "theoretical possibility" that British troops might not be involved.
"He has every reason to believe there will be a significant military contribution from the UK," he added.