House Republicans regularly bash President Barack Obama over his domestic agenda, but they are holding their fire when it comes to Afghanistan, an issue on which they often support the president — and even may have the final say when it comes to shaping a war funding bill.

Republicans generally support requests by military leaders for more funds or troop increases. But now that Obama may actually need GOP support to advance his Afghanistan strategy amid growing war fatigue among Democrats, some Republicans say their votes may be contingent on passing a clean bill.

“I would hope we would have leverage to not have it become a Christmas tree,— Appropriations ranking member Jerry Lewis (R-Calif.) said.

Lewis noted that Democrats originally attached funding for the Cash for Clunkers program to the war supplemental bill this year, a move that angered Republicans. While most lawmakers have yet to see details on Obama’s plan for Afghanistan, Lewis warned that any war funding bill must be clean if Obama wants solid GOP support.

“I think he’s going to have to rely on Republicans,— said Rep. Jack Kingston (R-Ga.), a member of the Appropriations Subcommittee on Defense.

Kingston and other Republicans concurred that while Obama will have their votes if he seeks funds for more troops, they have newfound clout in shaping any impending bill given the waning support among Democrats for sending more troops into combat.

“In the end, if you keep the bill clean, there will be no problem passing this,— Rep. Mark Kirk (R-Ill.) said. “But it won’t be with many Democrats on board.—

Democrats cautioned Obama against relying too heavily on members of the minority party.

“He certainly can’t rely on the Republicans,— Rep. Gene Taylor (D-Miss.) said. “They’ve thus far opposed everything he’s done, and I would imagine they would do so on this.—

Taylor on Wednesday was one of several Members who participated in a classified administration briefing on the situation in Afghanistan — a meeting that Taylor said left him with more questions than answers.

“I [just came] from a classified briefing that left me less certain about what the goals are than I was when I walked into the briefing,— he said. “I really do not believe [Obama] has articulated very well what it is we hope to accomplish long term and why this is worth one more American life and another billion dollars. Or even one more dollar.—

By contrast, Armed Services Chairman Ike Skelton (D-Mo.) exited the meeting urging lawmakers to give “serious consideration— to whatever requests are put forward by military leaders.

“U.S. national security and regional stability demand that we give Afghanistan the attention it deserves,— Skelton said in a statement. “Afghanistan can no longer play second fiddle to other national security concerns.—

But Republicans eager to go on the record supporting military leaders will have to swallow hard on the issue of cost.

“This war will cost a trillion dollars right off the top,— said Rep. John Murtha (D-Pa.), chairman of the Appropriations Subcommittee on Defense.

Murtha said a handful of high-level Republicans have told him privately that they agree with him on the need for clearer goals in Afghanistan before they could support sending more U.S. troops overseas.

Above all, the Pennsylvania Democrat said, military leaders must prove to both parties that they have a way to pay for their efforts. “The military tends to ask for more troops; whenever they have a problem, they just want more troops,— he said. “And they’re sending signals that they’re going to ask for this.—

Rep. Frank Wolf (R-Va.), the author of the bill that created the Iraq Study Group, on Wednesday floated the idea of creating a panel of nationally known figures to back the strategy in Afghanistan put forth by military leaders and to build public support for staying in the region.

But Murtha shot down the idea.

“They talk too much, they leak too much, they don’t consider the cost,— he said. “I deal with money. I know what the strain is on the military. … It’s all money.—

Key Democrats have already signaled an unwillingness to back more troop increases. Speaker Nancy Pelosi (D-Calif.) said last week that the House lacks the will to approve more troops.

Appropriations Chairman David Obey (D-Wis.), who refuses to even discuss the issue, appears intent on keeping his pledge not to pass any more war supplemental bills.

Murtha took aim at the Armed Services chairman for his unwavering support of military leaders’ requests.

“Skelton says you need more resolve. Resolve is not the problem. It’s money,— he said.

Echoing Murtha’s emphasis on money, some anti-war lawmakers are banking on Congress ultimately voting to pull troops out of Afghanistan because of excessive costs.

“Pretty soon, moon rocks are going to be cheaper than rocks from Afghanistan,— one leading liberal Democrat said. “It’s unsustainable financially. It may eventually be what usually happens in this town: Money trumps morality.—