A major war in the Persian Gulf could cost the United States $1 billion a day, while a protracted military stalemate will add hundreds of millions of dollars to the defense budget, defense analysts said yesterday.

The mushrooming U.S. military presence in the gulf could cost the Pentagon an extra $10 million to $15 million a day, according to several analysts, but a Defense Department spokesman said yesterday that "it's an ongoing operation and we don't have any figures yet."

President Bush, asked about the issue during a news conference yesterday, said he hoped to get an estimate from the Pentagon, "but I don't have any figures for you on that right now."

Should shooting start, all sources agree, the financial price would be astronomical. "We used to figure in the early '80s that a major war in Europe would cost about $3 billion a day, and that would be about $4 billion now," said Lawrence Korb, a Brookings Institution analyst and former assistant defense secretary. "Against the Iraqis, the cost would probably be about a quarter of that, maybe $1 billion a day."

Korb estimates that under current conditions, "the incremental cost of U.S. troops being in the gulf as opposed to {Forts} Bragg or Stewart, plus the additional cost to the Navy, you're talking about $300 million a month," based on a force of 25,000 men. Officials have said that under some circumstances, the U.S. force could go up to 200,000.

The Center for Defense Information, an organization of former military officers often critical of U.S. military spending, estimates that a force of 50,000 men, 270 Navy aircraft and 80 Air Force aircraft will cost about $438 million a month extra because of transportation costs, higher operating tempos and other factors. For example, an aircraft carrier battle group, such as the USS Independence and the six ships accompanying it in the Gulf of Oman, costs an extra $1.5 million a day, according to CDI's David Isenberg.

Several congressional staff members agree that Operation Desert Shield is expensive. "But the first thing to remember is that a big part of the bill has to do with military personnel pay -- and these guys get paid whether they're in Saudi Arabia or North Carolina," added an analyst for the Congressional Budget Office, which expects to have a cost estimate ready in two to three weeks.

Saudi Arabia and perhaps a liberated Kuwait would be expected to underwrite some of the costs, particularly for fuel, according to congressional sources. "I think the Saudis will do their part," President Bush said yesterday. Although the Saudis reportedly are wary of appearing to have hired mercenaries for protection, Prince Bandar bin Sultan, the Saudi ambassador, said, "I am sure that we will not disagree as friends over what needs to be done to share the burden overall."

In addition to pressuring foreign governments to support the embargo against Iraq, the Bush administration shows willingness to squeeze its friends for money. On Monday night, Bush called Japanese Prime Minister Toshiki Kaifu and urged Tokyo to "make as much of a contribution as possible," according to a Japanese Embassy spokesman here.

Japan's constitution forbids use of force to solve international disputes; the government is contemplating how to contribute beyond supporting the embargo against Iraq and occupied Kuwait, which together supplied 11 percent of Japan's oil this year. Three years ago, during the operation to protect oil tankers in the gulf against attack, Japan responded to Western demands for aid by financing a navigation system in the gulf, providing $850 million in grants, loans and credit to Jordan, and increasing the money paid to support U.S. bases in Japan.

U.S. officials say they would like to see similar contributions from wealthy allies, particularly since the United States has pledged to help Jordan and other small countries weather the financial hardship of the embargo. As in Japan, the issue appears to be under advisement. A spokesman for the West German Embassy, for example, said yesterday, "All I'm aware of is that we have, in our framework in NATO, decided to send a small flotilla to the eastern Mediterranean. That's all I know of a direct German contribution," although there has been discussion of helping Jordan.

The U.S. government faces substantial costs other than those tied to rising fuel prices and military operations. With most of its assets abroad frozen and virtually no oil revenue coming in, Iraq is expected to default on $2 billion in loans guaranteed by the Commodity Credit Corp. Under the program, Iraq became the largest foreign buyer of U.S. rice and a major customer for wheat and other grains.

Last year the CCC guaranteed $1 billion in Iraqi purchases and had promised another $500 million this year before the program was disrupted -- first by investigations into irregularities and then by the current crisis. "We're in line with other creditors for the frozen Iraqi assets," Sally Klusaritz, a U.S. Department of Agriculture spokesman, said yesterday.

But, beyond the price of oil, it is the cost of the massing military force in the gulf that seems potentially open-ended. As President Ronald Reagan's defense buildup in the 1980s demonstrated, operating a modern army, navy and air force is phenomenally expensive.

An F-15E fighter, for example, costs more than $4,000 an hour to fly, according to figures compiled by the Defense Budget Project. An Army division costs about $2.5 billion a year to operate in peacetime, according to the CBO, while a carrier battle group costs $1.1 billion and a wing of 72 F-16 fighters costs $250 million for salaries, fuel, spare parts and so on. The relatively quick and simple invasion of Panama last year cost $400 million, by one estimate. About 25,000 troops were deployed in that operation, almost half of them from U.S. military bases in Panama.

For the gulf operation, some costs appear inevitable. Late last week, for example, before troops began shipping out of Fort Stewart, Ga., for Saudi Arabia, the Army went on a shopping spree at a nearby K mart. Among the items on the list: 5,500 containers of foot powder, lip balm, suntan ointment and skin lotion; 2,400 cans of insect repellent; and 174,000 gallons of bottled water.

Staff writer Carlos Sanchez and staff researcher Lucy Shackelford contributed to this report.