Mr. Obama's proposal included some ideas favored by Republicans, although the Democratic president has little hope of winning over even a single Republican lawmaker. Republicans have demanded that he discard his proposals and start working with them on a new one.
However, a congressman who has played a key role in the long-running debate said he and 11 other Democrats will vote against the overhaul bill unless a provision subsidizing abortion is removed.
Rep. Bart Stupak, D-Mich., argued Thursday that the provision in the
Senate-passed version has language that would permit the federal government to "directly subsidize abortions."
The White House hopes that by including elements of Republican plans, Mr. Obama can win over Democratic lawmakers from conservative districts whose re-election hopes in November could be jeopardized by voting for the bill. If he can generate stronger Democratic support, congressional leaders can use parliamentary maneuvers to bypass Republican objections.
"I think he has succeeded in prying open a window of opportunity, but it's a very narrow window," said first-term Democratic Rep. Gerry Connolly. "And he and the leadership here had better clamber through that narrow window while they can."
In a speech Wednesday at the White House, Mr. Obama called on lawmakers to end a year of legislative struggle and angry public debate and enact legislation ushering in near-universal health coverage for the first time in the country's history. He called for an "up-or-down vote" within weeks under rules denying Republicans the ability to block the bill with a filibuster.
"At stake right now is not just our ability to solve this problem, but our ability to solve any problem," the president said. "And so I ask Congress to finish its work, and I look forward to signing this reform into law."
The president will begin campaigning for health care legislation next week with stops in Philadelphia and St. Louis, reports CBS News senior White House correspondent Bill Plante.
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Appearing before a select audience, many of them wearing white medical coats, Mr. Obama firmly rejected calls from Republicans to draft new legislation from scratch.
"I don't see how another year of negotiations would help," he said. "I believe the United States Congress owes the American people a final vote."
Asked to predict a timeframe, Health and Human Services Secretary Kathleen Sebelius said, "The dates and time frame are really up to the leaders of Congress." Sebelius, who appeared on CBS' "The Early Show" Thursday added, "but the urgency comes from the American public who is right now in terrible trouble."
Lawmakers were almost finished merging House and Senate versions of sweeping overhaul legislation when a special election in Massachusetts last month cost Democrats their filibuster-proof Senate majority, throwing the effort into disarray. Mr. Obama is attempting to revive it with one final push, but with Republicans united in opposition, there is no certainty about the outcome.
The effort appears most troubled in the House, where the legislation passed by a narrow 220-215 margin in November. Since then several Democrats have defected or departed, and all 254 who remain are eyeing November midterm elections and a restive electorate clamoring for more jobs and skeptical of the health overhaul effort.
"It's fragile," Democratic Rep. Joe Courtney said of the mood in the House. "It's getting close to the election."
Thirty-nine Democrats voted "no" on the House bill, and House Speaker Nancy Pelosi will likely need some of those to switch their votes. The legislative package now under consideration has less restrictive language on federal funding of abortion than approved by the House.
Nonetheless, Pelosi vowed to answer the president's call.
"Our families and businesses deserve reform that will create millions of jobs, strengthen Medicare, reduce our deficit and no longer deny care or drop coverage to those who need it most," Pelosi said. "We must act now."
Republicans said Democrats would be sorry.
"Americans do not want a trillion-dollar government takeover of health care stuffed with tax hikes, Medicare cuts and giveaways to Washington special interests," said House Republican leader John Boehner. "Not today, not tomorrow, not ever."
Mr. Obama's endorsement of an up-or-down vote sealed Democrats' intention to move forward under rules allowing for a simple majority vote in the Senate, thereby circumventing Republicans, who now command enough votes to deny Democrats the 60-vote supermajority normally needed to act.
At its core, the legislation still is largely along the lines Mr. Obama has long sought. It would extend coverage to tens of millions of uninsured Americans while cracking down on insurance company practices such as denying policies on the basis of pre-existing medical conditions. An insurance exchange would be created in which private companies could sell policies to consumers.
Much of the cost of the legislation, nearly $1 trillion over a decade, would be financed by cuts in future Medicare payments and higher payroll taxes on individuals earning more than $200,000 and couples more than $250,000.
In his latest changes Mr. Obama added some Republican ideas raised at last week's bipartisan summit, including renewed efforts on changes in medical malpractice and rooting out waste and fraud from the system.