War with Iraq appears a step closer after Tony Blair said he believed a second United Nations resolution on Iraq was "now probably less likely than at any time".
British troops in the desert
His official spokesman said that efforts were continuing to secure a diplomatic solution to the crisis - but accused France of "poisoning" the diplomatic process.
Government sources said efforts could continue into next Monday if necessary, but Downing Street said they could not "elasticate for ever".
Amid rising tension, the Queen has cancelled a visit to Belgium next week on the advice of the Foreign
Office because it was felt that it would not be appropriate for her to be out of the country "given the present circumstances".
Earlier Foreign Secretary Jack Straw condemned France's "extraordinary" intention to veto any further UN motion on Iraq and implied their action had made it more difficult to avoid war.
Chancellor Gordon Brown said he would back military action against Iraq without a second resolution if France used an "unreasonable" veto, arguing that Mr Blair should be given "100% support".
The leader of the British opposition, Iain Duncan Smith, met Mr Blair on Thursday morning and said he had been told a second resolution was "less likely than at any time before".
Mr Duncan Smith reported the prime minister as blaming the "intransigence" of France in rejecting Britain's efforts to find a compromise second UN resolution.
"That, and to a lesser extent the Russians, has meant that unaligned nations are finding it difficult to make a decision because if it is going to be vetoed anyway they are saying 'so what'," said Mr Duncan Smith.
"That means essentially military action has become more likely and with that in mind our thoughts and prayers and I'm sure those of everybody and those of my party are with our forces and their families at this time."
The same message came from Mr Straw - who added that everybody knew that when the UN agreed to resolution 1441 the words "serious consequences" meant military action.
Mr Straw also revealed that the UK was willing to drop part of one of six key tests for Iraqi disarmament - for Saddam Hussein to make a television broadcast admitting that he had lied about his weapons of mass destruction.
"If the only issue between us, our partners in the Security Council and Saddam Hussein is whether or not he makes a television broadcast, then we are happy to drop that," Mr Straw said.
"But of course there has to be a statement, in his native language, in Arabic, that he does accept that he has been in non compliance with a whole succession of resolutions since 1991."
The prime minister now faces the difficult scenario of committing UK forces to a war in circumstances with which at least one member of his own cabinet disagrees with.
A 75-minute meeting of the Cabinet on Thursday saw a number of minister raise "valid questions" but, said Mr Blair's spokesman, there had been "broad support" for the government line.
This included a promise of a further emergency meeting if and when the diplomatic process broke down.
It was the first Cabinet meeting since International Development Secretary Clare Short's recent outburst in which she branded him "reckless" and suggested she might quit the government if Britain joined a war without further UN backing.
She told the BBC that she might have "irritated" her colleagues with her outspokenness, but did not regret her comments.
"I said what I said because I was fearful that we were just going to end up in conflict without everything being properly attended to.
"I thought it was necessary to draw attention to these things. If this comes out right I will be happy, that is all I'm trying to achieve."
MPs will have an opportunity to voice support or dissent over Iraq during a debate and a vote on the issue of Iraq, Leader of the Commons Robin Cook announced on Thursday.
Meanwhile Liberal Democrat leader Charles Kennedy argued that the international community should redouble its efforts using a combination of inspectors and containment although he pledged support for UK forces in the event of action.
Kofi Annan, the UN Secretary General, said he had spoken to Mr Blair, who "seemed very genuinely looking for a compromise and a way forward".
"He also indicated to me that if, in his judgement Saddam Hussein and the Iraqi leadership were to meet the tasks set and one were to conclude that he was genuinely disarming, we should accept it," he told BBC's Newsnight.
"Of course, if he failed, then the consequences should follow."
On Wednesday the British ambassador to the UN, Sir Jeremy Greenstock, warned of serious consequences for the future of the UN if agreement could not be reached, saying: "Unless you use this repair job, the hole in the ship will sink the ship."