Washington ? Amid soaring budget deficits, President Barack Obama is running into congressional qualms over how to pay for his troop buildup in Afghanistan. Military strategy aside, the $30 billion cost is causing concern on both sides of the aisle.

Still, leaders in Congress predicted Wednesday that Obama would prevail in winning funding for the war escalation.

Some Democrats, favoring the 30,000 troop increase, are supporting a “war tax.” But the White House and most lawmakers appeared unwilling to take such a step.

Most likely, the federal government will simply increase its borrowing — as it has before.

The government has already shelled out a combined $1 trillion since 2001 for the wars in Afghanistan and Iraq.

And Pennsylvania Rep. John Murtha, a senior House Democrat who oversees military spending, predicted on Wednesday that Congress would pass a special $40 billion war spending bill early next year to pay for the added deployments. He said that he and other anti-war Democrats would not be able to stop it. But the money probably won’t come from a special tax increase.

House Minority Leader John Boehner, R-Ohio, said Wednesday that “raising taxes in the middle of a weak economy is a prescription for a disaster.”

Instead, he suggested taking unspent funds from Obama’s $787 billion stimulus package to pay for additional war costs — a proposal not likely to win many backers on the Democratic side. It’s hard to imagine Democrats agreeing to use leftover stimulus money or cutting programs they like to pay for a war many of them hate.

A reason that Republicans votes will be needed to advance the money bill is that dozens of anti-war Democrats are likely to oppose the measure whatever the financial cost.

House Speaker Nancy Pelosi, D-Calif., also has been cool to the tax proposal, while acknowledging “serious unrest” among Democrats over the growing cost of the war.

White House spokesman Robert Gibbs said whether the money would be requested through special legislation or through the regular budget process for the next fiscal year was “a bridge that has not been crossed.”

Obama said Tuesday night that troops would begin coming home in July 2011. But under heavy GOP questioning, Defense Secretary Robert Gates acknowledged at a Senate hearing Wednesday that the additional troops could be there longer if conditions did not improve.

Many liberal Democrats who are otherwise strong supporters of the president suggested the nation could be bogged down in an expensive Vietnam-like quagmire for years to come.

The $30 billion White House estimate means about $1 million for each service man or woman.

But some budget analysts put the price tag of the escalation at closer to $40 billion a year when related costs are added in, including increased civilian aid, efforts to expand the Afghan army and police and greater aid to Pakistan.

The total cost to the U.S. of the Afghanistan war will rise to more than $8 billion a month, up from $4.6 billion in the budget year that ended Sept. 30, said military analyst Anthony H. Cordesman of the Center for Strategic and International Studies.