Representative Bart Stupak takes part in a hearing on Capitol Hill in Washington. Stupak leads a group of a dozen Democrats who are opposed to health-care reform they say is not restrictive enough in funding for abortion. (Lauren Victoria Burke/Associated Press)

A dozen Democrats in the U.S. House of Representatives opposed to abortion say they are willing to bring down President Barack Obama's proposed health-care bill unless tighter language barring funding of the procedure is added.

Representative Bart Stupak, a Democrat from Michigan, told ABC's Good Morning America on Thursday he and 11 Democratic allies were upset that the health-care reform package now under consideration contained less-restrictive language on federal funding of abortion than a previous bill approved by the House in November.

"We're not going to vote for the bill with that language in there," he said. "I want to see health care, but we're not going to bypass some principles that we believe strongly about."

The language in the health-care bill that passed in Senate last year — and which the revised version builds upon — restricts the use of public funds for abortion services.

But the bill also calls for the establishment of an insurance exchange, a marketplace that can offer private insurance plans that may cover abortion if funds for the procedure come solely from beneficiary premiums. Stupak had earlier proposed an amendment, which failed in the Senate, limiting access to abortions for people receiving federal subsidies or who purchase insurance through an insurance exchange.

Health and Human Services Secretary Kathleen Sebelius, appearing on the same show, defended the bill, which she said in its final form will be clear "that this bill does not change the status quo on abortion."

"There will be no federal financing of abortion," she said.

Obama calls for quick passage of bill

Obama laid out a revised version of his health-care legislation on Wednesday and called on congressional leaders to end a year of legislative struggle and enact a plan that will bring near-universal health coverage for the first time in the country's history.

The revised legislation is an attempt to merge House and Senate versions of health-care reform bills. Obama also called for an "up-and-down vote" within weeks, a stipulation that would deny Republicans the ability to stall the bill in the Senate with a filibuster.

House Majority Leader Steny Hoyer said Thursday that Democrats would like to have a final vote on the bill by March 29, the beginning of the Easter break for Congress, but cautioned that the timeline is not set in stone.

Before the legislation can reach the Senate, however, it must first be approved by the House of Representatives.

Though Democrats hold majorities in both congressional bodies, the fate of the legislation is uncertain, as many Democrats are on the fence over proposed reforms, with some facing elections in the fall.

As well, differences between House and Senate versions need to be reconciled in a manner that will appeal to Democrats in both congressional bodies.

A House version of the bill that included Stupak's amendment narrowly passed by a vote of 220-215 in November, making the support from even a few representatives on the fence crucial to the bill's passage.

Republicans have already been clear that they intend to unanimously oppose the legislation and have called on Obama to restart the process.

But Obama resisted that call in his speech on Wednesday.

"I do not see how another year of negotiations would help. Moreover, the insurance companies aren't starting over. They are continuing to raise premiums and deny coverage as we speak. For us to start over now could simply lead to delay that could last for another decade or even more."

The revised proposal is expected to require most Americans to carry health insurance coverage, and bar insurance companies from denying coverage to people with medical problems or charging them more.

It would not include a publicly run insurance plan, however, but would allow the government to cap health insurance premiums "if a rate increase is unreasonable and unjustified."

The plan calls for much of the cost of the legislation, nearly $1 trillion US over a decade, to 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.

Obama met with more than a dozen Democrats from the House of Representatives at the White House Thursday to discuss the proposed legislation, including those who voted against it last year.

With files from The Associated Press