Driven by unanticipated combat, higher-than-expected troop levels and rising political pressure, the White House reversed course today and asked Congress for an additional $25 billion for the wars in Iraq and Afghanistan for the fiscal year that begins in October.

"While we do not know the precise costs for operations next year, recent developments on the ground and increased demands on our troops indicate the need to plan for contingencies," President Bush said in a statement on the request this afternoon. "We must make sure there is no disruption in funding and resources for our troops."

He said he was asking Congress to "establish a $25 billion contingency reserve fund for the coming fiscal year to meet all commitments to our troops and to make sure we succeed in these critical fronts in the war on terror." He said his administration later would seek a full supplemental request for fiscal 2005 "when we can better estimate precise costs."

Bush made the request after a meeting this morning in which he and Defense Secretary Donald H. Rumsfeld discussed recommendations from U.S. military commanders in Iraq and Afghanistan about their needs.

Bush included no war funding in his fiscal 2005 budget, and he had hoped to avoid such a request until after the November election, fearing a divisive, campaign-year debate over the war's conduct and future, Republican congressional aides said. Congress has already approved two wartime emergency spending laws totaling $166 billion, of which $149 billion went to Iraq.

But in recent weeks, military officials publicly stated that U.S. forces were already running into financial problems, and would likely run out of money even before Sept. 30, the end of the current fiscal year. Accounting tricks would likely patch those holes, they said, but it was unclear how the military would be able to wait until January or February, when the administration planned to detail its next war request.

Democrats -- and some Republicans-- have put increasing pressure on Bush to detail the cost of operations and to request additional funding as soon as possible. The Democrats used their weekly radio address Saturday to air a critique by 1st Lt. Paul Rieckhoff, an Army reservist who spent 10 months in Iraq.

"There were not enough vehicles, not enough ammunition, not enough medical supplies, not enough water," he said. "There was not enough body armor, leaving my men to dodge bullets with Vietnam-era flak vests. We had to write home and ask for batteries to be included in our care packages. Our soldiers deserve better."

White House budget director Joshua B. Bolten and Deputy Defense Secretary Paul Wolfowitz made an unscheduled trip to Capitol Hill this afternoon to lay out the request in a meeting with House Speaker Dennis Hastert (R-Ill.), Senate Majority Leader Bill Frist (R-Tenn.), House Majority Leader Tom DeLay (R-Texas) and House and Senate appropriations committee Republicans.

"It was a bit of a surprise for us," said one House Republican leadership aide.

Republican aides conceded today that the $25 billion Bush will seek is likely to be only the first installment. In February, Bolten said the president would seek as much as $50 billion next year. But that was when the Defense Department had expected U.S. troop levels in Iraq to be about 115,000 by now and to fall to about half that by the summer of 2005. Now, the Pentagon is preparing to maintain a force of 138,000 for at least the next 18 months.

House and Senate budget negotiators have already agreed to include $50 billion in the budget blueprint they are trying to complete for 2005, but defense experts say even that will fall short. One House appropriations committee aide, speaking on condition of anonymity, said the full cost of war in 2005 will be around $65 billion, more than two and a half times the president's request.

"Given the increased tempo of operations as seen in April and the need for the long-term deployment of troops, it is clear that this is not enough money," said Sen. Jack Reed (D-R.I.) "It is unfortunate that the administration spends so much energy and time in denying the fact they need any help."

Sophisticated munitions, combat intensity and the high cost of an all-volunteer Army have already made the Iraq war an expensive conflict. With an additional $25 billion, the war's total cost exceeds the inflation-adjusted costs of the Revolutionary War, the War of 1812, the Mexican-American War, the Spanish-American War and the Persian Gulf War combined, according to a war cost study by Yale University economist William D. Nordhaus.

At $174 billion, the Iraq conflict would be approaching the inflation-adjusted, $199 billion cost of World War I, a level the war will likely pass next year.

Such numbers figured prominently in the contentious debate last fall over Bush's $87 billion request for military and rebuilding activities in Iraq and Afghanistan. But a House Republican leadership aide said the debate this year will likely be less divisive. The last bill included nearly $20 billion in reconstruction funds that even many Republicans believed was excessive for an oil-rich nation like Iraq, the aide said. This time, the money will be devoted almost exclusively to U.S. troops and security needs.

Congressional aides said the White House changed tack when it became clear the debate over the war would be unavoidable. Leaders of the House and Senate armed services committees said they would include money for the war in their annual defense bills. And appropriators were expected to follow suit, with or without a request from the administration.

Indeed, Republican and Democratic aides on the appropriations committees said today the big fight will be holding the request down to the president's level. For weeks, Republicans and Democrats have been imploring Bush to send up a war request before the military was forced to juggle different accounts to fund combat operations.

"Forcing the services to piece together budgets is likely to have a deleterious effect on training, housing, recapitalization of equipment and, ultimately, morale," wrote 11 Democratic senators in a letter to Bush two months ago. "Our fighting men and women deserve better."

The White House would like to keep the request as a discreet, emergency spending bill, but appropriators will likely fold it into the larger defense spending bill to keep off extraneous pet projects that lawmakers would try to slip into such a "must-pass" measure in an election year, aides said.