WASHINGTON -The White House has reached a tentative agreement with union leaders to tax high-cost medical plans, one of the final obstacles in the way of President Barack Obama's health care remake, officials said Thursday.

Details of the agreement were not immediately available. The tentative deal was expected to be presented to congressional leaders Thursday as negotiators try to wrap up an agreement on core elements of the sweeping legislation as early as Friday.

The proposed tax has been a major sticking point because early versions from the Senate would have hit union members, who have negotiated generous health benefits, sacrificing higher wages. House Democrats were strongly opposed, and did not include the tax in their bill. But Obama favored the tax, citing the consensus opinion of economists that it would help hold down costs by nudging workers into less pricey coverage.

Union and Democratic officials spoke about the tentative deal on condition of anonymity because the talks were private.

Word of it came as the pace of negotiations quickened.

House Ways and Means Committee Chairman Charles Rangel, D-N.Y., told reporters that negotiators are pushing toward a broad agreement on the legislation by Friday, and would send the package to the Congressional Budget Office for its estimates. The agreement in principle would cover key issues such as how many Americans would get coverage, and how to pay for it. Certain issues, including restrictions on taxpayer funding for abortion, would be resolved later.

"We're shooting for tomorrow," Rangel said early Thursday after meeting with Speaker Nancy Pelosi, D-Calif., and other leaders. "We hope to have the whole thing, as much as we can have (for the budget office) to be able to start working." The budget referees must review the legislation before Congress can cast a final vote and send the bill to Obama.  (Emphasis added)

Officials familiar with the negotiations said Wednesday that options being considered to lessen the impact on union members included raising the threshold at which the tax would be levied — it's $23,000 for family plans in the Senate-passed bill — and exempting collective bargaining agreements negotiated before 2013 from the tax.

Under that scenario the tax wouldn't hit until union contracts were renegotiated, delaying its impact on most union health plans until perhaps 2015 or 2016. There was also discussion of lessening the impact of the tax in high-cost regions of the country — where insurance premiums cost more — by imposing the tax on a sliding scale.

Obama and Democratic leaders spent all day Wednesday working intensely to resolve differences between the House and Senate versions of the legislation, which would expand coverage to more than 30 million people now uninsured, bar insurers from denying coverage to people with medical problems, and attempt to rein in ruinous increases in health care costs.

Negotiators were to meet again Thursday at the White House, and Obama planned to go to Capitol Hill to make a personal appeal to House Democrats, who are being asked to make major concessions. Democratic bargainers were also considering seeking more money from drugmakers and other provider groups to help subsidize care for the uninsured.

Public support for the health care remake continues to drop, perhaps in part because of the messy debate in Congress, and lawmakers are feeling the pressure of other issues, from unemployment to ballooning budget deficits. In Massachusetts, the race to fill the seat of the late Sen. Edward M. Kennedy is turning into a referendum on health care overhaul, with Republicans hoping to capitalize on voters' misgivings.

Late Wednesday, Obama and senior Democrats emerged from marathon health care talks with a declaration that they had made tough gains — but no deal just yet. The same group of leaders was to meet again at the White House on Thursday.

House Democrats are uneasy over concessions they are being asked to make to preserve the 60 votes needed to pass the bill in the Senate. That includes dropping the government-run insurance option liberals have fought for and accepting some form of a tax on high-cost health insurance plans adamantly opposed by many House Democrats and by labor unions.

House Democratic leaders are pushing for more generous subsidies to help make health insurance affordable to a greater number of middle-class households, as well as other concessions.

To help pay for that, Democrats want health care providers to bear more of the cost, said lobbyists speaking on condition of anonymity because conversations within the industry were confidential. One said Democratic proposals include adding $10 billion to the $80 billion over 10 years that the drug industry had agreed to contribute, and raising the $20 billion in Senate-approved fees imposed on medical device makers by $10 billion.

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