Updated: 8:50 p.m.Senate Democrats appear to have bowed to the demands of Sen. Joe Lieberman (ID-Conn.) Monday evening, essentially agreeing to jettison a Medicare expansion provision that was to have been included in their health care reform bill.Though Lieberman’s repeated filibuster threats effectively forced Democratic leaders to abandon two key liberal priorities — the Medicare proposal and a public insurance option — he still refused to endorse the bill until he sees the rest of a proposed compromise, which was brokered by a group of five Democratic centrists and five liberals a week ago. The Medicare buy-in provision was originally floated as part of that tentative agreement, until Lieberman threatened Sunday to filibuster the bill over the proposal.“At this point because there’s been so much misunderstanding based on ideas that are thrown around, I’ve said to [Senate Majority Leader Harry Reid] and he’s agreed that I want to take a look at what’s in these alternative proposals before I sign on,— Lieberman said upon exiting a special caucus that was called largely to address his concerns. “Put me down tonight as encouraged at the direction in which the discussion are going.—Lieberman said he has not gotten an “explicit assurance— that the proposal to allow seniors aged 55 to 64 to buy Medicare coverage would be eliminated, but other Senators indicated it would not be part of the Senate health care bill.Senate Finance Chairman Max Baucus (D-Mont.) said that an official decision on the Medicare buy-in had not been made but that he expected it would be abandoned.“It’s just a matter of getting support from 60 Senators, and that seems to be a condition that’s necessary to get to 60,— Baucus said.Indeed, Democrats appear to have provisionally agreed to the change in an effort to ensure they will have a filibuster-proof 60 votes to pass the bill by Christmas, a timeline Democratic aides said was set by the White House. No Republicans support the measure, so Reid needs all 60 Members of the Democratic Conference to prevail.Lieberman’s filibuster threat over the Medicare proposal surprised and angered Reid and other Senate leaders Sunday, considering the self-described Independent Democrat told them he was willing to entertain the provision when the group of 10 Democrats began considering it more than a week ago.Lieberman acknowledged Monday evening that he had told Reid as well as Sens. Charles Schumer (D-N.Y.) and Mark Pryor (D-Ark.) the leaders of the group of 10 that he was “open to the idea, but I needed to see what it exactly was going to be and what it would cost. And, you know, as the days went on and I got a sense of it but I still haven’t seen it I just, as I said to Sen. Reid on Friday and I said to Sen. Schumer, Sen. Pryor before they went into that final meeting the other night the more I understood about what they were trying to do the less I liked it.—He added that he believes the bill already helps people between the ages of 55 and 64 adequate access to affordable health insurance coverage.“I thought I made myself clear all along,— Lieberman said of his conversations with leaders. “Obviously, I regret any misunderstanding. Again, I wasn’t the only one in the Democratic caucus who was concerned or opposed to the Medicare buy-in. There were many more.—Though anger at Lieberman appeared to be simmering under the surface, Reid tried to defuse the situation in the caucus by pre-emptively acknowledging Members’ frustration with Lieberman, one source said. Reid told Members that he understood how they felt, but reminded them of the many GOP filibusters Lieberman has helped them overcome this year, the source said.Members exited the caucus saying they primarily discussed the importance of passing a historic bill that would help ease the burden of health care costs and extend insurance to millions of uninsured.“We’ve been elected by the people of this country to govern. They’ve invested in us their confidence to be president. We’ve got majorities in the House and in the Senate. Our job is to govern,” said Sen. Tom Carper (D-Del.).One Senate Democrat said the newest Democrat in the caucus party switcher Sen. Arlen Specter (Pa.) got a round of applause for saying of the Republicans, “Don’t let these obstructionists win. I came to this caucus to be your 60th vote.—Reid spoke to reporters after the special caucus, but took no questions.“I’m confident that by next week we’ll be on our way to forward this bill to the president,— he said.He reiterated his intent to keep the contents of the proposed moderate-liberal deal a secret until the Congressional Budget Office returns an official cost estimate. That CBO score is expected sometime Tuesday, aides said.But just as Reid appeared to solve one problem with the bill, another issue reared its head.Sen. Roland Burris (D-Ill.), who previously has threatened to vote against any bill that does not include a public option, took to the floor immediately following the closed-door meeting to reiterate his stance and express “deep reservations about what I have heard up to this point.—“Until I see more, I can only say again what I have said from the very first day of this debate so many months ago: I am committed to voting for a bill that achieves the goals of a public option, competition, cost savings and accountability,— Burris said. “I will not be able to vote for lesser legislation that ignores these fundamentals.—David M. Drucker and Jessica Brady contributed to this report.