Correction Appended

Two key Senate moderates on Sunday cast grave doubts on a health care compromise intended to unite the Democratic Conference behind thelegislation.

Sens. Joe Lieberman (ID-Conn.) and Ben Nelson (D-Neb.), important votes for Senate Majority Leader Harry Reid (D-Nev.), said on CBS’ “Face the Nation— that they have problems with the Medicare buy-in, which would allow people as young as 55 to participate in the program.

Lieberman said he would have “trouble— voting for the provision and suggested that it cannot get 60 votes. “Opposition to it has been growing as the week went on,— he said.

Nelson, who already said he will not vote for the overall health care bill because of abortion language within it, said the Medicare buy-in could lead to “a single-payer plan— that he opposes “even more directly than the public option.—

Nelson said he agreed to the “deal— not because he necessarily supported the language, but in order to keep the legislative ball rolling. “I withheld my decision on that until we see the numbers and see how it all works,— he said. “I want to be a friend of the process.—

Lieberman stated that the agreement was in fact never a “deal,— but instead something “interesting enough to send to the Congressional Budget Office.—He called on Democratic leaders to remove the buy-in provision and add more cost-cutting measures. “There’s a good basic bill here— but “we’ve got to stop adding to the bill,— Lieberman said. “I think the only way to get this done before Christmas is to bring in some Republicans.—

No Republicans currently back the legislation.

Nelson also appeared to call for a bipartisan bill. “Every piece of landmark legislation has had bipartisan support,— he said. And Nelson asserted that efforts to fix the abortion language so that it would be suitable to him are “a tall order for people.—

But Sen. Jay Rockefeller (D-W.Va.), who also appeared on “Face the Nation,— expressed optimism about the bill’s prospects, saying that when Senators are forced to look at the legislation in its totality they will drop parochial concerns.

“I think we have tremendous momentum,— he said.

Correction: Dec. 13, 2009

The article misstated that Sen. Joe Lieberman was a member of the group of 10 liberal and moderate Democratic Senators that worked on the compromise. He was not.