Rupert Cornwell: Blair follows Churchill's footsteps to the White House in pivotal moment for military history

Visits to Washington by British prime ministers have provided some of the pivotal moments in history. Yesterday's discussions between George Bush and Tony Blair belong squarely in their number.

Back in 1943, Franklin Roosevelt and Winston Churchill spent much of May honing a strategy for the defeat of Hitler. There were weekends at Camp David – then called Shangri-la – where the two talked on the terrace drinking highballs as the smoke of their cigars and cigarettes kept the mosquitoes at bay. Churchill managed to persuade Roosevelt to postpone the second European front, which the Americans wanted to open later that year.

At the White House, Churchill, with his late hours and copious drinking, became almost too much of a good thing. At one point Roosevelt sought out the prime minister, only to find the great man in his natural splendour, emerging pink and steaming from a bath. A British Prime Minister, Churchill is said to have quipped, "has nothing to hide from an American President". Six decades on, the circumstances are oddly similar.

George Bush, the reformed binge drinker, will not take even a sip of wine. Neither man smokes, and dinner will be sparing and early. But once again, a hinge moment in hinge moment affairs is at hand and, conversationally at least, Blair will hide nothing from Bush.

At his very first meeting with Bush in February 2001, long before 11 September, the Prime Minister raised the issue of Iraq and Saddam Hussein's defiance of the United Nations.

Today, that crisis is approaching its climax, and once again eyes are glued on a British prime minister and an American president in the White House. Blair and Bush formulaicly reiterate that war is not yet inevitable, that there are still a few weeks left to persuade the Iraqi dictator to disarm or go into exile. There are no deadlines they say. But no one is fooled. The broad timetables of war are on the table.

If diplomacy fails, an invasion of Iraq is unlikely to be delayed much beyond mid-March. But like Churchill, Blair's main diplomatic preoccupation is time – maybe just the time between late February and mid-March, a small further interval in which Bush should go the extra mile to secure a second UN resolution specifically endorsing war.

The US may be the mightiest country on earth, but privately the British tell Washington that Bush must build the widest coalition possible. If anything, Blair has an even greater need of the cover afforded by another UN resolution, to mend the split with France and Germany and shore up public opinion at home.

The stakes are enormous. Collateral damage could include the stability of several Middle Eastern regimes, the viability of the UN and Europe's efforts to build a common foreign policy.

Iraq is only part of the crisis. Just as during the critical periods of the last world war, these first months of 2003 could prove a crucial point in the long struggle against terrorism and the spread of weapons of mass destruction.

Administrations in Washington rarely manage to concentrate on more than one crisis at a time. Yesterday, Iraq was the focus. But just like Churchill and Roosevelt in 1943, Blair and Bush are having to fight on several fronts. For proof, consider events of the past 24 hours.

North Korea may be moving nuclear fuel rods out of storage at its Yongbyon facility, US spy satellite photos suggested yesterday, as it prepares to convert them into weapons grade plutonium. If so, is diplomacy the answer or pre-emptive military strikes that could trigger a new Korean war? The explosion that killed 15 passengers on a bus yesterday in Afghanistan demonstrates that Taliban and al-Qa'ida are nowhere near extinct. The 28 Pakistanis arrested in Naples with explosives and maps are suspected Osama bin Laden followers. Bin Laden himself may still be alive.

For Churchill and Roosevelt everything was clearer cut. Germany was an enemy that had to be defeated; Britain and the US (and the Soviet Union) were the only countries that could do it.

Today, the defeat of Iraq may cause more problems than it solves, and merely fuel the terrorists' fanaticism. And despite the statement of support from European countries, Bush and Blair are uncomfortably alone in the front line against Iraq.