The range is wide both because it is unclear how long any military action will take and because it is unknown whether allies will share the costs with the U.S.

"It's impossible to predict," said David Wyss, chief economist at Standard & Poor's. "You're talking a range of outcomes from $40 for a barrel of oil to the end of Western civilization."

Even a victory, if the financial cost is high, may deepen U.S. deficits and slow the economic recovery, Democratic lawmakers have said. A supplemental budget request to cover the war will include cash to prevent and defend against potential terror attacks, Homeland Security Secretary Tom Ridge said after a White House meeting today. A request may be made within two days.

Federal Reserve Chairman Alan Greenspan has told Congress that uncertainty over Iraq imposed "formidable barriers" to an economic turnaround. Bush's proposal for the fiscal year beginning Oct. 1 projects a record $307 billion deficit in a $2.23 trillion government budget for the fiscal year beginning Oct. 1, not including the cost of armed conflict with Iraq.

The Bush administration has given widely varying cost estimates. President George W. Bush's former chief economic adviser, Lawrence Lindsey, in September pegged the cost of a war at between $100 billion and $200 billion.

1991 War

A week later White House budget director Mitch Daniels disputed Lindsey's estimate, saying a war with Iraq would cost about the same as the $61 billion for the 1991 Persian Gulf conflict. The U.S. spent about $7 billion, while allies, including the U.K. and Saudi Arabia, paid the remainder.

The $61 billion cost in 1991 would be about $80 billion in today's dollars.

The Bush administration is preparing a $95 billion spending request to help pay for the war this fiscal year, with some of the funds geared toward rebuilding Iraq, the New York Times reported last month.

Defense Secretary Donald Rumsfeld has said that it is impossible to predict the cost accurately.

"If you don't know if it's going to last six days, six weeks or six months, how in the world can you come up with a cost estimate?" Rumsfeld said Feb. 27. "The people who tried estimate those things for the Gulf War were flat wrong by an enormous amount, and it makes no sense to try to do it."

`Highly Uncertain'

White House spokesman Ari Fleischer said no decisions have been made about the size of a supplemental request. The request would cover costs to help Iraq establish a democratic government after the war, he said.

"Estimates of the total cost of a military conflict with Iraq and such a conflict's aftermath are highly uncertain," the U.S. Congressional Budget Office wrote in a report last year saying the war cost may range from $21 billion to $272 billion.

War costs will total $10 billion the first month, and $8 billion every month after the initial attack, the CBO said in a report March 13 on federal spending plans.

"The incremental cost following combat operations could vary from about $1 billion to $4 billion a month," the CBO said in the study posted on its Web site.

Democrats

Democrats on the House Budget Committee said that assuming an attack were to last 30 days to 60 days and involve 125,000 troops, the cost for that phase of the operation would reach between $48 billion and $61 billion.

A larger force of 250,000 troops would cost between $75 billion and $93 billion, the Democrats said.

Some private economists say much-higher costs are possible, once the costs of the impact of a slower U.S. economy and a resulting loss in tax revenue to the Treasury are factored in.

Wyss estimates that the direct costs of prosecuting a war against Iraq to range between $50 billion and $100 billion a year, with costs to rebuild Iraq adding another $50 billion to $100 billion total.

If oil prices were to surge after an invasion, the indirect costs could loom large, he said. Assuming a "worst-case" scenario of oil prices jumping to between $50 and $60 a barrel, the economy could slow and result in up to $300 billion in lost revenue for the government, he estimates.