The White House reached a tentative agreement with union leaders early Thursday to tax high-cost insurance plans, officials said, removing one of the major stumbling blocks in the way of a final compromise on comprehensive health care legislation sought by President Barack Obama.

Complete details of the tentative deal were not immediately available, although the White House was expected to present it to senior lawmakers later in the day. Union leaders also were returning to the White House.

Rep. Joe Courtney, D-Conn., who led the opposition to the tax in the House, said the agreement involves several measures that would ease its impact. Among them: excluding the value of dental and vision benefits when applying the tax as well as raising the $23,000 threshold at which it would take effect for families.

Union officials are also pushing to provide that anyone who makes $200,000 or less would be excluded from the health plan benefits tax, a concession that would also benefit employees who are not unionized.

In a win specifically for union members, negotiators were working out a plan to delay the tax from being imposed on collectively bargained health plans for several years.

White House spokesman Robert Gibbs said the Obama administration and Democratic congressional leaders think they are "very, very close" to surmounting remaining obstacles in the way of finalizing health care legislation.