House Democratic leader Steny Hoyer indicated Democrats were short of the 218 votes needed to pass the reform bill but said "we're very close." House members were warned the final vote could be Sunday or even later in the week.

Democrats spent the day cajoling dozens of party moderates concerned about abortion and immigration provisions in the bill, as well as its $1 trillion price tag and its possible effect on budget deficits.

"There are many people who are still looking to get a comfort level that this is the right thing to do," Hoyer said. "We're trying to answer any concerns they might have."

The sweeping overhaul, President Barack Obama's top domestic priority, would spark the biggest changes in the U.S. healthcare system since the creation of the Medicare health program for the elderly in 1965.

House Republicans are united in opposition to the measure, designed to rein in costs, expand coverage to millions of uninsured and bar insurance practices such as denying coverage to people with pre-existing conditions.

Republicans object to new taxes to pay for the changes and the potential impact on the budget, and say it is too much government meddling in the private healthcare and insurance markets.

Obama is expected to visit the Capitol on Saturday to rally Democrats to support the House bill, which was bolstered on Thursday with endorsements from powerful lobbying groups for doctors and older Americans.

Failure in the Democratic-controlled House would be a huge political blow to Obama. Democrats can afford to lose 40 of their 258 House members on the healthcare vote, but the ranks of potential defectors is even larger.

Democratic Representative Frank Kratovil said he would vote against the bill because it does not do enough to curb the growth in costs and he is concerned about its effect on small businesses.

He said he had not heard from Obama or House Speaker Nancy Pelosi since his decision on Thursday to oppose the bill, but had been talking to plenty of other House members.

NO POINT IN LOBBYING

"At this time there is not much point in lobbying me," he said. "I am a 'no.'"

If the bill passes the House, the action would move to the Senate which is preparing its own version. Obama wants to sign a bill by year's end, but Senate Democratic leader Harry Reid has indicated that deadline might slip.

House Democrats plan to open debate on Saturday morning and Hoyer said he expected a final vote on Saturday night. But he warned that Republicans might delay it, and he said the House would keep working through Sunday or later if needed.

"We're going to complete this effort," Hoyer said. "We will consider this to conclusion."

House liberals dropped plans to introduce an amendment backing a single-payer government-subsidized healthcare system. House Republicans will be given a vote on their alternative healthcare plan before debate on the Democratic bill.

The House bill would require individuals to buy insurance and all but the smallest employers to offer health coverage to workers. It also would provide subsidies to help purchase insurance and would eliminate the industry's exemption from federal antitrust laws.

Congressional budget analysts say the bill would extend coverage to 36 million uninsured people living in the United States and would reduce the budget deficit by about $100 billion over 10 years.

About 40 Democratic moderates have threatened to vote against the measure unless language is strengthened to ensure no federal subsidies are used to pay for abortions.

In an effort to resolve the dispute, Democratic leaders are expected to incorporate an amendment by Representative Brad Ellsworth, an opponent of abortion rights, into the rule setting the terms of the debate.

That amendment would guarantee access to insurance plans that agree to refrain from covering abortion. It has been attacked as unsatisfactory by other anti-abortion Democrats and groups like the National Right to Life Committee.

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