Washington (CNN) -- Senate Democrats are preparing to drop a compromise health-care plan that would allow 55- to 64-year-olds to buy into Medicare because of opposition from Connecticut Sen. Joe Lieberman, two senior Democratic sources said Monday.
"It's what the White House wants, and there aren't many other options that allow us to finish by Christmas," said one source.
Lieberman, an independent who caucuses with the Democrats, has emerged as the majority party's main obstacle to its efforts to get a health care bill through the Senate before Christmas. He ratcheted up his public opposition to the bill Sunday by threatening to join a Republican filibuster if the legislation contains either a government-run public health insurance option or a proposed alternative that would expand Medicare to people as young as 55.
"I think the danger always is you try to add too much onto a bill," he told reporters Monday evening. He said he supports the "core" of the bill, including tighter regulations on private insurers, but he wants Democrats to "take off some of this stuff that runs the risk of creating federal debt, and moves toward a government takeover of insurance, which I think would be bad."
Unanimous Republican opposition so far means Senate Democrats need all 60 votes in their caucus to close debate on the sweeping health care bill. Final passage of the bill would then require only a simple majority of 51.
Lieberman supported letting older workers buy into Medicare in 2000, when he was the Democratic vice presidential candidate, and as recently as September in comments to a Connecticut newspaper. But he said Monday that the idea was "no longer necessary," since the Senate bill includes subsidies to help people 55 and older buy insurance coverage before they become eligible for Medicare.
"I was suggesting various ideas for health care reform that did not involve the public option, and that was the focus at that time," he said. "But the important thing is I'm for health care reform, and if we get together, we're going to deliver a health care reform bill that will provide the ability to get health insurance to 30 million people that don't have it now."
Lieberman spokesman Marshall Wittmann said that now, "We have a huge national deficit and a program that analysts indicate is in dire fiscal straits in 2009."
Senate Democrats held an emergency meeting Monday night to discuss the issue, which threatens to derail the Obama administration's push for a sweeping reform of U.S. health insurance. Although a final decision was not made at Monday night's meeting, a second Democratic source said a final decision could be made at a White House meeting Tuesday between the Senate's Democratic majority and President Obama.
"I think there is a fundamental understanding of the direction we're going in," said Sen. John Kerry, D-Massachusetts.
Before the meeting, liberal Democrats Tom Harkin of Iowa and Jay Rockefeller of West Virginia indicated that the Medicare buy-in would likely be dropped. While they didn't like the idea, they suggested they would support a health care bill anyway.
Democrats "may have to do what Mr. Lieberman wants," Harkin said.
The Medicare expansion was part of a package of provisions announced by Reid last week as an alternative to a government-run public health insurance program, which lacked enough support among Democrats to break a filibuster. Negotiated by a team of 10 Democratic senators -- five liberal and five moderate -- the compromise package was hailed by Reid, Obama and others as an important step forward in the health care debate.
The package also would allow private insurers to offer nonprofit health coverage overseen by the government. But many senators have reserved judgment on the compromise proposal until the non-partisan Congressional Budget Office provides its analysis of how much it costs.
Senate Majority Leader Harry Reid would discuss no specifics of a bill after Monday night's caucus, telling reporters he would wait until the CBO finished its estimate of a revised bill's cost. But he said the measure "saves lives, saves money and saves Medicare."
"I am confident that by next week we'll be on our way to forward this bill to the president," he said.
Most Democrats support the public option as a nonprofit competitor to private insurers that would expand coverage and bring down prices. Republicans and some moderate Democrats, along with the health insurance industry -- one of the major employers in Lieberman's home state -- oppose a public option, calling it a first step toward a government takeover of the U.S. health care system.
Lieberman first expressed possible opposition to the health care bill in late October, saying he would join a GOP filibuster if the measure contained the public option. Asked about Lieberman's position then, Reid said: "Joe Lieberman is the least of Harry Reid's problems."
Another potential obstacle for Reid is moderate Democrat Ben Nelson of Nebraska, who said Sunday he cannot support the Senate bill without tighter restrictions on federal funding for abortion. The Senate last week defeated an amendment proposed by Nelson and two other senators that would adopt tougher language on abortion funding contained in the House health care bill.
A compromise on the abortion language is possible, said Nelson, one of 10 Senate Democrats who negotiated in private last week on the public option compromise.
If the Senate eventually passes a health care bill, its version will have to be merged with the version the House of Representatives passed in November, which includes a public health insurance plan. The final bill would then need approval from both chambers before going to Obama to be signed into law.
Obama and Democratic leaders have said they want the bill completed this year. The Senate would need to finish its work this week to leave a realistic chance of meeting that schedule.
CNN's Dana Bash and Tom Cohen contributed to this report.