Guardian writers below explore the key issues confronting Mr Blair in the crucial next days:

Can he persuade George Bush to remain flexible and give more time?

The Bush administration has let deadlines slip and relaxed seemingly entrenched negotiating positions several times over the past few weeks of gruelling UN negotiations over Iraq.

However, administration officials made clear yesterday that one deadline remains intact. Washington will wait no longer than the end of March.

It is a matter of the president's credibility, the officials say. At the end of January, Mr Bush vowed that Saddam Hussein had "weeks not months" and the White House briefed journalists to take that statement literally. In other words, there was less than two months remaining for Iraq to disarm fully and voluntarily. "The president has not changed his position," an official said.

Ari Fleischer, the White House spokesman, insisted that a UN vote take place this week and rejected a Cameroonian proposal to extend the deadline facing Baghdad by more than a month, repeating several times that there was "not much time" left.

"Any suggestion of 30 days, 45 days is a non-starter," he said.

However, its flexibility to date may have more to do with the problems the Pentagon has been having putting its troops into place than its commitment to a diplomatic solution. Many observers in Washington say it is military logistics that have been driving the pace of diplomacy, not the other way round, in which case there may be another fortnight for talks.

Yesterday, one of the most important units in the Pentagon's war plans, the 101st airborne division, unloaded its Apache helicopters from transport ships docked in Kuwait, but another important element of the strategy is still stranded at sea.

The tanks of the 4th infantry division are still on board ships awaiting a second Turkish parliamentary vote on allowing it to use Turkey as a launching pad for a northern offensive. If that vote goes against the US, the Pentagon will have to reconfigure its forces for a plan B, which could take more than a week.

But reworking the war plan in the event of a British withdrawal would be even harder. The defence secretary, Donald Rumsfeld, raised that possibility for the first time yesterday. But the prospect of fighting without the British is worrying enough for the administration to give London some clout in its talks with Washington.

Can he convince the so-called 'swing six' wavering countries on the security council to back a second resolution?

Now that the "undecided six" on the security council have said that they want more time and more "benchmarks" for Saddam to disarm, Mr Blair's attempt to bridge the yawning gap between America and the rest of the world has become even more troubled.

Diplomats always presumed that the six elected members of the council - Pakistan, Chile, Mexico, Cameroon, Angola and Guinea - would acquiesce in the face of American pressure. Britain knew that none was enthusiastic about war but also calculated that each had sufficient incentive not to provoke the ire of the world's only superpower.

But each has its own domestic audience to play to. The Pakistani regime has seen huge demonstrations over the weekend. Regional elections bolstered the opposition in Mexico and almost the entire political class is opposed to the war in Chile.

But Britain said yesterday that it remained confident that three of the six - Angola, Cameroon and Guinea - would vote for a second resolution, while a government source said signs were good that it could get two more - Mexico and Chile.

Pakistan continued to insist yesterday its vote was no longer up for grabs and it will abstain.

With Spain and Bulgaria also on board, that would give the US and Britain nine votes out of 15, and a claim to have a moral majority for war, even if they fail to secure the resolution because of the French veto.

The swing six said yesterday they wanted not only an extra 45 days for an ultimatum for Iraq but that the UN chief weapons inspector, Hans Blix, rather than the US and Britain should preside over whether Iraq complies with new disarmament demands.

The UK and US expressed reluctance last night to go along with the 45-day timeframe or return responsibility for triggering war to Mr Blix.

Failure to secure a majority of nine would be a disaster for Mr Blair, leaving him unable to tell his ministers and party he has a moral majority and leaving him without the necessary legal cover for an invasion of Iraq.

How is he going to defuse the threat of a Russian and French veto?

Russia's foreign minister, Igor Ivanov, reiterated that Moscow would oppose the second resolution yesterday, adding for the first time that Russia was against the resolution as it would cause a regime change in Iraq by force.

None of this rules out a last-minute compromise. Western diplomats are said now to be homing in on Russia, in the hope that if President Vladimir Putin can be persuaded not to use his veto, that would have a knock-on effect on the other refusenik, France.

A resolution that plays down the "serious consequences" of non-compliance, while setting a deadline - perhaps as late as early April - for Iraq to meet certain specific and attainable disarmament targets, may tease out a Russian abstention.

Mr Blair's difficulties with Russia pale beside his battle now with France. Paris will prove almost impossible to budge as long as any proposed text contains an automatic trigger for war. Jacques Chirac, de facto spokesman for the international anti-war axis, promised he would vote against a resolution authorising war "under any circumstances".

Yesterday, a foreign ministry spokesman softened that position, saying of the proposed British compromise amendment that it was "a new development. We've indicated we are open to dialogue".

But France's bottom line remains that war is always the worst solution. It might accept a series of tests or benchmarks that Saddam must pass to prove he is disarming, but not an ultimatum. "We want no ultimatum. We want no element of automaticity" the spokesman said.

Opposition is mounting from his own party and the public at home. What must he do to contain it?

Mr Blair will face a tense and anxious Commons at prime minister's questions today. Both he and his party know that if he fails to secure a second UN resolution, the repercussions for his leadership will be immense.

After his noon grilling in the chamber, Mr Blair may call wavering Labour backbenchers to his rooms below Big Ben. But the need to return to his round of global phone calls in pursuit of the vital resolution is likely to curtail the time available for MPs.

Privately Mr Blair admits that, despite all his efforts, he is failing to persuade public opinion of the case for disarming Saddam Hussein by force if necessary.

But the section of opinion which could prove lethal to his survival if he fights without UN sanction lies within his own party.

The mood is intense. John Reid, his combative party chairman, constantly addresses conferences, unions and party groups, albeit with mixed results. The defence secretary, Geoff Hoon, has fitted in party meetings. Jack Straw's Foreign Office team talks to backbenchers.

Government whips do most work to keep tabs on rebels and wavering MPs. "They ring very regularly and ask 'what do you feel about it?'" says one MP.

Mr Blair needs to keep his cabinet onside. Most are giving their leader the benefits of their doubts, and Mr Blair is careful to keep them up to speed on developments. "He's kept us informed, and what he says in private is what he says in public," says one.

But Clare Short threatened to resign because she felt her concerns were not being taken seriously. Robin Cook may also quit.

And a new threat emerged last night when the leftwing Campaign Group of MPs effectively urged Mr Blair to resign "if he is not prepared to stand up to George Bush" and avoid war with Iraq.

Blair still has a mountain to climb in persuading the British public that war is justified. What is his media strategy for doing so?

In the battle for public opinion, Mr Blair will continue to seek out his critics.

In the past week he has appeared before hostile audiences on MTV and on ITV's Tonight with Trevor McDonald, when a grim-faced prime minister was on the receiving end of a slow handclap from anti-war women.

Earlier he appeared before an angry and articulate group on a special Newsnight recorded in Gateshead.

Downing Street has not despaired at the opposition Mr Blair has met. "He's shown he's not afraid to put his case to a hostile audience. And the core argument he has established is that this policy is not being pursued for ulterior motives or for craven motives. No one is now saying it's being done for oil or because he's George Bush's poodle," says one adviser.

Officials point to a modest shift in public opinion. Yesterday's Populus poll for the Times showed 19% willing to back a war without UN sanction (11% a month ago) with 24% still against war in any situation. The shift is from the "only with UN permission" column, 62% a month ago, 52% now.

Such figures underline that Mr Blair is keen to clutch at small straws and still keen to engage in the fight. Press conferences, Commons debates, regular TV and newspaper interviews, as well as engagements like ITV's will remain part of the campaign.

For a party leader long taunted for not doing anything without first making sure the focus groups would approve Mr Blair is in the odd position of defying his party, his polls and his focus groups.

The big question: If a second resolution falls, Blair will have to decide whether to go to war in any case. Would it be legal for Britain to do so?

Going to war without a new UN resolution backing military action would be illegal despite claims to the contrary made by Britain and the US. This is the near-unanimous view of international lawyers, and was supported this week by the UN secretary general. "If the US and others were to go outside the security council and take unilateral action they would not be in conformity with the [UN] charter," Kofi Annan said.

Some international lawyers say war is justified - with or without any further resolution - because Saddam has not honoured the UN-backed ceasefire terms after the 1991 Gulf war.

However, the widespread view in Whitehall is that a new, strongly-worded UN resolution was needed before a war could be regarded as being backed by international law.

This view is believed to be shared by Lord Goldsmith, the attorney general, who yesterday had a meeting with Mr Blair and Mr Hoon.

Mr Blair may be hoping that he can persuade MPs that a draft resolution backed by a majority on the security council would amount to a "yes" vote, irrespective of any veto by one or more of the permanent members. While this might strengthen the prime minister's position politically, and even morally, it will make no difference to the legality or legitimacy of a war.

Legally, any claim by Mr Blair that a French veto would be "unreasonable" is irrelevant. And with a veto there will be no new resolution.

Resolution 1441, by which ministers have laid so much store, speaks only of "serious consequences" if Saddam Hussein does not disarm. The phrase falls far short of an instruction to UN member states to use "all necessary means" - the traditional UN term for armed intervention.