Updated: 8:28 p.m.

Senate Majority Leader Harry Reid (D-Nev.) hit a serious snag Thursday night in his push to get a health care reform measure finished by Christmas when he was faced with the prospect of losing a key vote to rid the Senate floor of a must-pass Defense spending bill.

But Reid may have salvaged his timeline when anti-war Sen. Russ Feingold (D-Wis.) appeared to agree to vote with all other 59 members of the Democratic Conference to kill a GOP-led filibuster of the bill. Sixty votes are needed to end a filibuster.

Feingold said he is merely considering changing his position on the defense legislation, although his fellow Democrats said they expect him to vote with them when the vote occurs early Friday morning.

“I haven’t formally decided. I have not finally decided. I am listening carefully to the arguments about how this is an attempt to derail the health care bill by simply using the Defense appropriations bill when they have every intention of passing the bill,— Feingold said. “It’s merely used at this point, and it appears — I’m listening to the argument that’s being used — as a wedge simply to force us not to be able to pass health care.—

A cheer went up right as the closed-door Democratic Caucus adjourned, with Sens. Max Baucus (Mont.) and Tom Harkin (Iowa) confirming on their way out that it was in response to Feingold announcing he would vote for the defense bill.

“The applause was for Russ Feingold,— Harkin said. “He’s very torn, he’s never supported these wars. He said a long time ago he was never going to vote for this. We all knew that. … But he got up and said what the Republicans are doing cannot be allowed to go on, and so he’s going to vote with us.—

Shortly after the Caucus meeting, Feingold issued a formal statement indicating he will vote for cloture on the defense bill.

“I do not support the defense funding bill and I will vote against it. But I am not going to be part of a partisan and cynical effort to delay passage of the defense bill in order to block the Senate fromconsidering health care reform. I will decide how to vote on healthcare when the final bill is before the Senate. But the Senate should be allowed to continue debating and voting on health care reformlegislation.—

Reid initially was willing to lose Feingold’s vote, because Senate Appropriations ranking member Thad Cochran (R-Miss.) had agreed to vote with Democrats, Democratic aides said.

But Cochran withdrew his support Thursday, in what appears to be the latest move by the GOP leadership to prevent Democrats from passing health care legislation before Christmas.

Reid spokesman Jim Manley issued a terse statement Thursday night, with harsh words for Cochran — though he did not name the Senator.

“Unfortunately, despite the assurances given by a Republican Senator that he would vote for the defense appropriations bill, it now looks like that may not happen,— Manley wrote in an e-mail. “Even though this one Republican Senator assured us every step of the way that he would support the DoD bill, he has now gone back on his word to join the Republicans in obstructing at all costs.—

Most Republicans do not actually oppose the Defense bill, but they have been attempting to delay its passage in the hope of also delaying a final vote on health care legislation by Christmas Eve.

To insulate himself against a potentially crippling delay in the health care debate, Reid refiled a motion to end debate, or invoke cloture, on a motion to proceed to the health care bill. The Senate already voted on that question before Thanksgiving, but if Democrats cannot end debate on the Defense bill they would need to vote on the health care bill again.

That cloture vote to return to the health care debate would occur on Saturday, with a vote on the motion to proceed sometime on Sunday. That would appear to put Reid’s timeline for passage by Christmas Eve in jeopardy since he is likely to need all the time from Saturday to Thursday to overcome GOP objections to the bill and pending amendments.