WASHINGTON -- House and Senate negotiators are closing in on a deal to resolve a years-long battle over legislation governing domestic spying powers.

In what could be a major breakthrough, the deal would resolve one of the thorniest issues: whether telecommunications companies should get immunity for cooperating with government surveillance after the Sept. 11, 2001, attacks.

The compromise, which is gaining support from both sides, would kick the issue to a secret national-security court. Earlier versions of the legislation wanted to grant telecom companies blanket retroactive immunity from lawsuits.

Even if it takes hold, such a deal would face a number of hurdles before becoming law. The first is whether House Speaker Nancy Pelosi (D., Calif.) will allow it to come up for a vote on the House floor.

The divisive politics of surveillance could also derail the compromise. As House and Senate Democrats forged ahead Thursday in negotiations, congressional Republicans blasted House Democrats, accusing them of stalling.

The compromise is largely being negotiated between key Democratic lawmakers and administration officials.

If the emerging compromise comes to fruition, it would settle a battle that has raged between Democratic lawmakers and the administration since 2006, when the administration's program of surveillance without court orders was revealed. In August 2007, Republican lawmakers outmaneuvered their Democratic counterparts to pass a temporary expansion of surveillance powers, which expired in February.