LAS VEGAS (AP) - Nevada's senators are blocking confirmation of President Bush's pick to lead nuclear waste disposal efforts at Yucca Mountain.

Sen. John Ensign, R-Nev., said Wednesday that he and Sen. Harry Reid, D-Nev., have placed holds on Ward Sproat, the administration nominee to direct the Energy Department's Office of Civilian Radioactive Waste Management.

Ensign, who met with Sproat on Nov. 2, said he and Reid will relent on Sproat "once we can get answers about where the administration is going" on nuclear waste. Reid had no comment.

Energy Department spokesman Craig Stevens said Bush administration officials "will work with senators ... to remedy their concerns."

The Senate Energy and Natural Resources Committee approved Sproat's confirmation Wednesday by a voice vote, sending it to the Senate floor. But senators can invoke procedural holds to block final action on nominees and legislation.

The Energy Department got approval from Bush and Congress in 2002 to entomb the nation's most radioactive nuclear waste at Yucca Mountain, 90 miles northwest of Las Vegas. The project has been without a Senate-confirmed leader since Margaret Chu resigned in February. Paul Golan, the principal deputy director, has been serving as acting director.