British diplomats at the United Nations are putting forward proposals aimed at securing wider support for a new resolution setting a deadline for Iraq to disarm.
UK ambassador Greenstock is to clarify proposals
They are reported to include a series of key tests which Baghdad will have to meet within a set time limit if it is to avert war.
The initiative comes after US and UK efforts received a double blow on Monday from France and Russia, which announced they would use their vetoes to block any resolution that authorised war.
UK Prime Minister Tony Blair criticised the move, saying: "If countries talk about using a veto in all sets of circumstances, the message that sends to [Iraqi leader] Saddam [Hussein] is: 'You're off the hook'."
Deadline, possibly 10 days, for Iraq to make strategic decision to disarm
17 March deadline to be postponed
Destruction of banned weapons
Evidence of previous claims of destroyed weapons
Interviews with Iraqi scientists abroad
Mr Blair has said he is working "flat out" for a second resolution - focusing on swaying six undecided members of the UN Security Council.
On Tuesday, one of them, Pakistan, confirmed its intention to abstain from the vote.
President George W Bush telephoned eight world leaders on Monday to press the moral case for war.
The Security Council is expected to discuss the UK initiative on Tuesday, but a vote is not expected until Wednesday at the earliest.
The latest British ideas appear to be a slight modification of the draft resolution put forward by the UK, US, and Spain last week.
UK ambassador Jeremy Greenstock told reporters at the UN in New York on Monday that they were "still in examination".
"There are people who want greater clarification," he told reporters in New York.
However, the proposals are said to include giving Iraqi leader Saddam Hussein a deadline - possibly 10 days - to make a strategic decision to disarm after which key tests would be applied.
These are believed to encompass allowing Iraqi scientists to be interviewed abroad, destroying banned weapons and providing documentary evidence of any such destruction in the past.
Bush has been working the phones
The initiative also envisages moving the Monday deadline for Iraq to disarm - contained in the current draft - to a later date.
The BBC's Greg Barrow at the UN says that, at this stage, any compromise is welcome if it can start to heal the diplomatic rift at the UN.
The chasm widened on Monday when President Jacques Chirac of France said Paris was ready to veto any resolution authorising war.
Russia also threatened to use the veto against the draft "in its current form" - leaving open the possibility of change in Moscow's position.
"We're under no illusions about France," said a White House official, "we would not be at all surprised if France stayed with a 'no vote' to the end."
But efforts to get a majority of the Security Council on board and thus to win a small moral victory continue apace, says the BBC's Justin Webb in Washington.
President Bush's spokesman has been comparing the moral principle underlying America's actions with the recent failure of the Security Council to stop civilians being killed in Rwanda and in Kosovo.
Mr Bush spoke to Chinese President Jiang Zemin on Monday - but Beijing repeated its opposition to war.