The hand of history will lie heavily on the shoulders of the leaders of Britain, America and Spain when they meet in the Azores today. It may not rank alongside the Casablanca summit of January 1943, when Franklin D Roosevelt and Winston Churchill met in Morocco to demand the unconditional surrender of Germany and Japan. But it is the pivotal moment in the Iraq crisis. Despite the publicly expressed determination of Washington and London to explore what remains of the possibilities of a peaceful settlement or a second resolution through the United Nations, it is a council of war. By this time next week that war may have started.

This is also a pivotal moment for the UN. Agreement on a second resolution to follow November’s 1441 now looks improbable. Jacques Chirac has boxed himself into a veto come what may. That seems to have made any further efforts to get a second resolution futile and has helped to extricate Tony Blair from his own domestic political crisis. Compared with 1991, when security council backing was sought for the first Gulf war, there has been relatively little arm-twisting of the smaller nations. Mr Chirac has been responsible singlehandedly for shutting down the UN route and, in the process, for throwing the future of the body into question.

On its website, the UN describes the demise of its predecessor with wonderful simplicity. “The League of Nations,” it says, “ceased its activities after having failed to prevent the second world war.” The UN will not cease its activities for failing to prevent a second Gulf war, but its role will be diminished. America will be reluctant to pursue that route again. The security council, a strange mix of the powerful, the once-powerful and the minnows, will never be seen in the same way again. Perhaps this was inevitable. The council has authorised military action on only three occasions: Korea in 1950, Iraq in 1991 and Afghanistan in 2001. In the case of Kosovo and more than 100 other conflicts, the UN remained silent. Its clear-cut approval may be helpful but it is not essential.

Perhaps it was unwise of Mr Blair to think that the UN route would work. After all, resolution 1441 came on the back of 16 previous resolutions, all of which Saddam Hussein flouted. In the end the prime minister had little choice. If he is facing cabinet resignations now and a backbench rebellion, it would be hard to see how he could have survived had he not pursued the UN route and a peaceful settlement. It was also a failure of diplomacy not to judge France’s tactics better. It was assumed France would behave as it always has done: strut, protest and eventually cave in. But post-cohabitation Chirac is a neo-Gaullist creature, full of ambitions to lead Europe, to frustrate Britain’s role on the Continent and to deny the United States an unchallenged role as world leader.

Fortunately for Mr Blair, the French president has overplayed his hand. The approach that won Dominique de Villepin, his foreign minister, applause at the security council last month, has been undone in Mr Chirac’s clumsy hands. Public opinion in Britain now sees the French approach for what it is: naked national interest. Mr Blair, on the political ropes after Clare Short’s pledge last weekend to resign in the event of war without a second resolution, was rescued by the French president and by the realisation in his own party that he remains far and away its best electoral asset. That does not mean, as some in Downing Street would have it, that the next mountain to climb after Iraq should be to join the euro out of some perverse post-war act of appeasement to the Franco-German alliance (if anything, this crisis illustrates the dangers of reckless European integration). It does mean that talk of a leadership challenge is far-fetched. Ms Short may go and many Labour supporters would regret it. Robin Cook, the leader of the Commons, is also shaping up for a pointless gesture. In the grand scheme, both would be small earthquakes in Westminster.

Mr Blair’s strategy has been to keep America engaged in the world. It would have been easy after September 11 for the United States to have become aggressive and isolationist, lashing out like a wounded animal at its enemies in periodic raids and then retreating to its own shores. That has not happened and much of the credit must go to the prime minister as well as George Bush. Not everybody in the US administration has favoured that approach, and Donald Rumsfeld’s boast last week that America could go it alone against Iraq showed that the defence secretary sometimes challenges the French president for gaffes. But the line has held.

America’s engagement is demonstrated by today’s summit. The president’s commitment on Friday to a “road map” for peace to end the Israel-Palestine conflict was further evidence. Mr Bush has been sensitive to the prime minister’s needs. The administration lost patience with the UN process some weeks ago but mainly for the sake of Britain has been prepared to pursue it to the last. Mr Blair is genuine when he insists that a peaceful settlement was pursued in good faith. While Washington was sceptical, he thought the security council could be won over. But he was also sure that a time limit had to be set on the process. Delaying indefinitely would not only play into Saddam’s hands but would also prolong the uncertainty that has led to wild swings on the world’s stock markets and is undermining economic confidence.

That point has now been reached. “This has gone on long enough,” said Condoleezza Rice, America’s national security adviser. Jack Straw, the foreign secretary, thought a few weeks ago that war would be averted. Yesterday he admitted: “The prospect of military action is now much more probable.” In the Gulf the troops, warships and planes are ready to go.

Saddam is a dangerous tyrant who has invaded Iran and Kuwait and attacked Israel and Saudi Arabia. He has used chemical weapons, not just in the war with Iran but also against his own people. Four million Iraqis have fled his regime and tens of thousands more of his opponents are dead or in jail. He has yet to prove he has destroyed 8,500 litres of anthrax, let alone the material to produce 26,000 litres more. He has 360 tons of bulk chemical warfare agent, including the deadly nerve agent VX gas. As his people have become impoverished, he has persisted with efforts to acquire weapons material from other countries. He is a danger to us all.

Nobody wants war. As that fine warrior the Duke of Wellington observed: “Next to a battle lost, the greatest misery is a battle gained.” There will be casualties on both sides. Sometimes, however, there is no alternative. Avoiding war means allowing Saddam to keep his weapons of mass destruction. It would encourage other rogue dictators to reach for the nuclear trigger. So war it has to be. And soon.