WASHINGTON — Lawmakers charged with merging the House and Senate versions of the National Defense Authorization Act decided on Tuesday to drop a provision that would have explicitly barred the military from holding American citizens and permanent residents in indefinite detention without trial as terrorism suspects, according to Congressional staff members familiar with the negotiations.

The Senate approved that amendment — sponsored by Senators Dianne Feinstein, Democrat of California, and Mike Lee, Republican of Utah — in a surprise vote last month. While it appeared to be a rare step to bolster protections for domestic civil liberties, rights groups opposed it because it did not cover other categories of people so they feared that it would implicitly open the door to using the military for domestic police purposes.

Lawmakers are expected to pass the compromise version of the annual military authorization act this week. In addition to counterterrorism issues, the huge bill covers a range of military and national security matters, including a 1.7 percent pay raise for the troops and the legislative imposition of new sanctions on Iran.

The White House has threatened to veto the bill over several provisions that the conference committee kept. But it was not clear whether President Obama will do so; in previous years he made similar threats only to sign it anyway, in part because lawmakers can attach identical provisions to spending bills that are difficult to veto.