Blair is playing for high stakes, and he needs Chirac to come to his rescue

It's not too glib to say that his future may be decided not in the White House, nor in No 10, but in the Elysée

Tony Blair flies to his talks on Iraq with President Bush knowing that he is facing the most perilous period of his premiership yet. As he also knows, the times are long gone when merely being seen as an honoured visitor in Washington serves to add lustre to his image at home. If anything, to judge from some of the polls, the very opposite could now be the case. In his party, not to mention the wider British public, the deep disquiet about impending war remains unabated, despite the remarkable robustness Blair showed in the Commons yesterday.

But then he is hardly going for a glorified photo-opportunity. The business is deadly serious. Partly he will seek to help the President to underline his message of Tuesday night, not least for the benefit of Saddam Hussein, that the only consequence of a failure to back down is war. Partly he will no doubt be engaged in the nitty gritty of planning that very war, and, you can only hope, just what would kind of Iraq would follow it. But partly, it safe to assume, there are reasssurances he will seek, and arguments he will put, in the privacy of one-to-one contact about when and how the war should start, if there is one.

The ringing applause for the President's warning that "the course of this nation does not depend on the decisions of others" cannot drown out the fact that Mr Blair would much prefer a second United Nations resolution, for all he is prepared to contemplate an invasion without it. And here the clear message should surely be that the momentum generated by the toughening challenges to Iraq in Hans Blix's report to the UN this week be at least allowed to build to critical mass. This isn't simply the elastic demand "for more time" that so enrages Washington. Logic, as well, as the need to meet the minimum demands of public opinion, requires it.

Maybe, Colin Powell's Adlai Stevenson/Cuban Missile Crisis moment next week, when he shares new intelligence with the Security Council on Saddam's unconventional weaponry (and the so far vague claims of links between Iraq and al-Qa'ida that Washington and London were suddenly seeking to talk up yesterday) – will be enough to persuade doubters such as the French, of whom more in a moment, that war is necessary. But Blix remains trusted, in a way that no politician can be. This week he shifted more of the burden of proof on to Saddam, having, according to diplomats, reached something of a turning point when his inspectors uncovered 3,000 documents on uranium enrichment in the home of an Iraqi scientist. If so, what possible justification can there be for not allowing him the time he evidently thinks he needs – and which may be vital to yield unanimity on the Security Council?

Further, daunting as it will be, given the brusque responses he has received on the subject during previous trips to Washington, Mr Blair should use all the leverage he can muster to press the President to revive hopes of a Middle East peace process. Mr Blair believes in this cause, and not only because he sees the urgency of persuading the Arab world that the West is not applying double standards by invading Iraq while allowing Israel to deal with the Palestinians as it thinks fit. This won't be easy. Whatever coalition the freshly mandated Ariel Sharon succeeds in forming – and the signs yesterday were that, despite his entreaties, it would not include the wounded, though far from extinct, Israeli left – the omens for the "peace plan" he himself promises are hardly encouraging.

First he insists that Yasser Arafat should be moved and the violence stopped before talks can begin. In contrast, the European view – and here Blair, the Northern Ireland process fresh in his mind, is closer to the EU than to the US – has been that neither are sensible to impose as preconditions. For if Sharon chooses to hold firm to his public insistence on "no negotiations under fire", it gives the most militant Palestinian groups such as Hamas an effective veto on whether talks can take place. (Indeed, one shred of comfort from the Israeli elections is the success of the secularist Shinui party, since this latter point is not lost on its leader, Tommy Lapid, even though he, too, is a hardliner on not dealing with Arafat.)

But even supposing that Sharon could somehow either fulfil or abandon both these preconditions, there is still no sign that he envisages more than an offer well below the minimum threshold of what any Palestinian leader could accept. As long as he remains Prime Minister it isn't easy to see this stance changing without concerted US pressure. Yet Washington continues to make what Lord Hurd described this week in a thoughtful speech on Iraq as "its most serious mistake" by putting on hold any "sustained and insistent initiative towards an even-handed peace between Israel and the Palestinians". The evidence of Tuesday night, namely a dismally platitudinous one-sentence reference to the issue in the State of the Union speech, holds out little hope that the mistake is going to be reversed.

Of course, if Blair were to secure any success on that one conflict that inflames the Arab world like no other – and it's a bleakly big "if" – it would also go a long way to stilling the threatened revolt at home, one that, in the worst-case scenario, could even make Blair dependent on (by no means unanimous) Tory support to see an invasion through. Some Labour MPs are torn between their hatred of Saddam, asking themselves if this really is about oil, and worrying as Clare Short did aloud yesterday about civilian casualties. At the same time, highly attuned as he is to the multiple insecurities of the voters, Blair will need to do more to convince them that war on Iraq will reduce rather than increase the risk of terrorism at home. Above all, he needs specific UN backing for any war.

Here, the President of France remains critical. If the French were, after much huffing and puffing, finally to vote for war, then Blair's political problems – though they would hardly vanish – would be much easier. If Jacques Chirac were to accept the Blair-Bush doctrine that UN Resolution 1441 is self-enforcing, even if – say – China were to pledge to veto a resolution, then the worries might also ease, provided, that is, Chirac was ready to send his own forces to Iraq. Either could well happen; the unwillingness of Chirac to be left behind should not be underestimated.

But if Chirac were to mount a sustained campaign against a US-led war, then Blair's difficulties would be greatly magnified, at real risk to his own standing. Certainly, Blair's moral belief that Saddam poses a global threat that cannot be ignored remains unswerving. More politically, there is also a sense in government that unless something turns up – like the fondly hoped for flight to Libya by Saddam – a point of no return has been reached: that he cannot now credibly pull Britain back from the brink. Of course, a short war and a stunning success would dispel the doubts. But the stakes are very high.

Perhaps it's not too glib to say that Blair's future may be decided not in the White House, nor in No 10, nor in the British Treasury, where an alternative candidate – albeit on Iraq a fully supportive one – awaits events, but in the Elysée.

d.macintyre@independent.co.uk