Democratic leaders in the U.S. House of Representatives hustled on Thursday to count votes and round up support for a sweeping healthcare overhaul that was headed to a close floor vote on Saturday.

Failure in the Democratic-controlled House would be a huge political blow to President Barack Obama, who has made an overhaul of the vast $2.5 trillion healthcare system his top domestic priority.

Obama planned to visit the Capitol on Friday for a pep talk to House Democrats before the vote. House leaders have struggled to win over some party moderates with lingering concerns about the bill's cost and its provisions on abortion.

I think it's going to be close, House Democratic leader Steny Hoyer said of the vote, but he expressed confidence the measure would get the 218 votes needed to pass. House Democrats hold 258 seats in the chamber.

Asked if she had the votes lined up, House Speaker Nancy Pelosi said: We will.

Republicans are united in opposition to the sweeping overhaul, which is 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.

If the healthcare 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.

About 1,000 protesters opposed to the healthcare reform effort gathered on the lawn outside the Capitol, waving yellow Don't Tread on Me flags and signs, including one reading Stop the Obama-nation of America.

The push for the House healthcare bill was bolstered on Thursday by the endorsement of AARP, a powerful lobbying group for older Americans with 40 million members.

BILL HELPS SENIORS

The lobbying group said the House bill would help seniors pay for their prescription drug coverage and strengthen Medicare, the government-run health program for the elderly.

We can say with confidence that it meets our priorities for protecting Medicare, providing more affordable health insurance for 50 to 64-year-olds, and reforming the healthcare system, Nancy LeaMond, executive vice president, said.

The American Medical Association, which represents doctors, was expected to endorse the measure later on Thursday. The American Cancer Society also announced its support for the House bill.

The overhaul would spark the biggest changes in the U.S. healthcare system since the creation of the Medicare program for the elderly in 1965.

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.

House Democratic leaders are trying to address concerns by some members who want to be sure federal subsidies are not spent to pay for abortions. Democrats who support abortion rights want to ensure the bill does not exceed current restrictions on using federal money to finance abortions.

The Senate's version of a healthcare bill has been bogged down as Democratic leaders await cost estimates from congressional budget analysts and search for an approach that could win the 60 votes needed to overcome Republican procedural hurdles.

Both the House and Senate bills include a government-run public insurance option that Obama and supporters say would create competition in the insurance market. Critics say it would lead to a government takeover of the sector.

If the two chambers finally pass their bills, differences in the two would have to be reconciled before a single reform bill would go to Obama for his signature.

(Additional reporting by Andy Sullivan; Editing by Patricia Wilson and Vicki Allen)

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