George W. Bush trudged through the first half of his State of the Union speech, a predictable boilerplate of tax-relief proposals, social-program fiddles and promises of a better economic tomorrow.

But when he got to the part about terrorism and Iraq, his voice grew stronger, his gestures more emphatic and his delivery more assured. His jaw set in resolve, his eyes wet with the passion of the moment, he came to his peroration with all the fervour of a Baptist preacher.

And no wonder. Some time in the next few weeks, Mr. Bush will make the hardest decision any leader can face: the decision to send his people to fight and die.

What is more, he will do so in circumstances unlike any other in recent U.S. history. The United States is not under direct attack. Nor is there any evidence that its target, Iraq, intends to attack Americans.

If he orders U.S. forces into battle against the regime of Saddam Hussein, it will be to prevent a possible, potential, future attack. That makes this a highly unusual — and, in much of the world, hugely unpopular — enterprise.

"Why all the hurry?" ask Mr. Bush's critics at home and abroad. Why not wait until the evidence is clearer, the threat more direct, the danger more imminent?

Tuesday night, the U.S. President gave his answer. The United States is in a race against time.

Terrorists involved in, or inspired by, Sept. 11 are set on killing great numbers of Americans. Rogue regimes are developing weapons of mass destruction.

If these two come together, the result could be a cataclysm that would dwarf the horrors of that September.

"Imagine those 19 hijackers with other weapons, and other plans — this time armed by Saddam Hussein. It would take just one vial, one canister, one crate slipped into this country to bring a day of horror like none we have ever known."

Mr. Bush himself has imagined it many times over.

Ever since Sept. 11, 2001, Mr. Bush and his security advisers have shared a waking nightmare. If the threat of weapons of mass destruction and the threat of suicidal megaterrorism should fuse into one, the United States would face a peril that even its vast military would be powerless to stop.

Preventing that nightmare from becoming reality is what drives Mr. Bush, and he does not believe he has the luxury of time.

Much has been said about his determination, which shines through in his every word. But his sense of urgency is just as strong.

"I will not wait on events while dangers gather," he said in last year's State of the Union address. "I will not stand by as peril draws closer and closer."

This year, he echoed, "We must act before the dangers are upon us."

The risk of the action Mr. Bush is contemplating — a pre-emptive war in the cockpit of the Middle East without local allies and with little unequivocal international support — are obvious and great.

But Mr. Bush fears the future more than the near present. He has weighed the risk of war against the risks of waiting, and found the second greater.

If terrorists and weapons of mass destruction are allowed to come together, he said, "all actions, all words, all recriminations would come too late."

Washington strives for peace, he said, but "a future lived at the mercy of terrible threats is no peace at all."

No one now can doubt the haste — the ticking clock in the back of his mind — that animates Mr. Bush. But can he persuade the rest of the world to share it?

A year and half after Sept. 11, the idea of a catastrophic attack on the United States or its allies by a terrorist group armed with weapons of mass destruction still seems far-fetched to many other nations and many Americans as well.

The polls show that if the country must go to war, most Americans would far prefer to do it with allies at their side.

Mr. Bush would too. But Tuesday night he made it clear, once again, that he would go it alone if he has to — as he very well may.

"The course of this nation does not depend on the decisions of others," he said, to thunderous applause. "Whatever action is required, whenever action is necessary, I will defend the freedom and security of the American people."

Mr. Bush almost shouted those words. He means them.