With two influential Senate Democrats coming out in support of a troop increase in Afghanistan, the window of opportunity for Vice President Joseph Biden and his liberal allies on Capitol Hill to make the case for an alternate approach appears to be rapidly closing.

Biden, former chairman of the Senate Foreign Relations Committee, and a handful of prominent House and Senate Democrats have been urging President Barack Obama against sending additional combat troops to Afghanistan. Instead, they argue, the administration should focus on building up the Afghan military and civilian government while also turning an eye toward Pakistan, where many analysts believe the greatest threat to U.S. interests exists.

But Republicans, who have largely been Obama’s political base on military issues this year, have been pressing him to back his generals.

Senate Appropriations Chairman Daniel Inouye (D-Hawaii) on Wednesday joined Intelligence Chairman Dianne Feinstein (D-Calif.) in arguing that a troop increase is the best strategy for success in Afghanistan. They suggested Obama heed the advice of military commander Gen. Stanley McChrystal, who has suggested some 40,000 more troops may be needed in the region.

Following his recent trip to Afghanistan on Tuesday, Inouye issued a statement, saying that “at this time, I believe General McChrystal’s assessment of the current situation and his conclusion, including his assessment that coalition forces must have more daily contact with the people of Afghanistan, is correct and is what is needed if we are to achieve security and stability in Afghanistan.—

During a Sunday appearance on CBS’ “Face the Nation,— Feinstein made similar remarks, arguing: “I don’t know how you put somebody in who is as crackerjack as Gen. McChrystal, who gives the president very solid recommendations, and not take those recommendations if you’re not going to pull out. If you don’t want to take the recommendations, then you put your people in such jeopardy,— Feinstein said.

Democrats and Republicans alike said this week that the issue appears to now be about how many troops Obama should request, rather than whether he should request additional troops at all.

“The counterterrorism strategy is off the table now. Withdrawal is off the table now. It gives more weight to the McChrystal recommendations,— Sen. Lindsey Graham (R-S.C.) said.

Sen. Ben Nelson (D-Neb.), a key moderate lawmaker, agreed, saying, “I think there’s no question that there will be more troops. It’s a question of what the mix will be.—

A source close to the Biden camp argued that it is not surprising that Feinstein — and to a lesser degree Inouye — has come out in support of a troop increase. However, this source, who asked not to be identified, acknowledged that thus far Biden and his Senate allies — Armed Services Chairman Carl Levin (D-Mich.) and Majority Whip Dick Durbin (D-Ill.) — have not done an adequate job of galvanizing like-minded Members.

“It’s not so much that we’re losing people. The problem is that we’re not picking anyone up,— the source said.

With that in mind, Biden and his Senate allies can be expected to begin making a push to rally support in the next week to 10 days, Democrats said. Several Democrats noted that with health care and climate change legislation dominating the debate, most lawmakers have not yet fully focused on Afghanistan. And to some extent Members haven’t had to since Obama has been taking his time to make a decision on a troop increase.

Sen. Jack Reed (D-R.I.), a member of the Armed Services panel and an influential voice on military issues within the Democratic Conference, said he supports Obama’s decision to carefully evaluate the situation.

“I think we need to work through the analysis,— Reed said.

Still, several Senate Democrats privately acknowledged that time is not on the side of opponents of a troop increase. “Members of Congress being what they are, the longer they take … the more likely it is people will come to their own opinions. And those may not be what the president wants,— a senior Democratic aide warned.