If George W. Bush goes ahead with his plan to build a missile-defence system for the United States, it will:

• Cost the American public from $30-billion to $50-billion;
• Raise the risk of a new global arms race;
• Sour relations with Russia and China;
• Seriously annoy U.S. allies such as France and Germany.

To take on all this trouble and expense, Mr. Bush must have a pretty good reason for going ahead, or so you might assume. In fact, there is no such reason. Missile defence is the solution to a problem that may not even exist.

Unlike the big weapons systems of the past, missile defence is not designed to counter an attack from some military behemoth or global rival to U.S. power. Even the wildest advocates of missile defence do not claim the system could halt a mass missile attack from Russia or China. Instead, missile defence is aimed at "rogue" countries -- small, radical, unpredictable nations that might chuck a missile or two at New York or San Francisco.

A commission headed by former U.S. defence secretary Donald Rumsfeld concluded in 1998 that if Iran, Iraq or North Korea decided to develop ballistic missiles and fit them with nuclear or biological warheads, they could "inflict major destruction on the United States." Since then, the alarms have grown even louder. "The threat is here today," Defence Secretary William Cohen said last March. "If it's not here right now, it will be here tomorrow."

Really? Let's look at the facts.

Apart from the five big nuclear powers, 33 countries have ballistic missiles. But, so far, not a single one has a long-range missile capable of reaching the United States. Most ballistic-missile countries have only short-range missiles such as the out-of-date Scud made famous by the Persian Gulf war. These have a range of less than 1,000 kilometres, far short of what is required to reach U.S. targets.

True, at least three hostile and unpredictable countries -- Iran, Iraq and North Korea -- have been trying to get missiles with a longer range. But will they succeed? And even if they do, are they crazy enough to fire one at the United States?

There is strong reason for doubt on both counts. Iraq was forced to dismantle many of its Scuds after the gulf war. Today, hemmed in by international sanctions and impoverished by an oil embargo, it would be hard-pressed to build anything capable of reaching the United States.

Iran has tested a medium-range missile with a range of 1,300 kilometres and is thought to be working on one with a range of more than 3,000 kilometres. But it isn't there yet, and the technical challenges of producing a long-range rocket -- better alloys, more sophisticated fuels -- are daunting.

Besides, Iran's relations with the United States have been warming since the election of reformist President Mohammed Khatami.

That leaves North Korea. A radical Marxist state that has often engaged in terrorism, North Korea shocked the world when it test-fired the Taepodong-1 missile in August of 1998, sending it over Japan and into the Pacific Ocean. U.S. experts said it was the first step in an attempt to build a missile that could hit Alaska, Hawaii or even the U.S. West Coast.

Missile-defence advocates practically jumped with glee. See, they crowed, there really is a rogue-nation missile threat. But, as even the sheltered Mr. Bush must know, things have changed a lot since then.

After pressure from the United States and Japan, North Korea suspended further missile tests. North Korean leader Kim Jong-il told visiting U.S. Secretary of State Madeleine Albright this fall that the Taepodong-1 test was his country's last.

The Albright visit was the latest step in a gradual warming of relations between North Korea and the rest of the world, highlighted by South Korean President Kim Dae-jung's historic visit to the North earlier this year.

Even assuming that Mr. Kim is lying and that he manages to obtain long-range missiles, it seems doubtful he would ever use them against the United States. Any leader that did so could count on a devastating U.S. response that would mean the end of his regime and probably his life.

If Mr. Bush wants to spend $50-billion to protect Americans from a threat as remote as a missile attack by a suicidal madman, he might as well equip every American with a personal lightning rod, too.

Iraqis or North Koreans who want to deal a blow to the evil Americans are much more likely to put a nuclear bomb in a tramp freighter and sail it into San Francisco Bay or put poison gas in the New York subway. It would be a lot easier, technically, and a lot less likely to draw a U.S. counterattack, because the source of such an attack would be harder to trace.

Before Mr. Bush spends billions of dollars, upsets U.S. allies, alienates Russia and China, and courts an new arms race, he should at least have to show that the United States is facing a real threat. The evidence, so far, is slim.