A longtime Republican foe of this year's planned closing of military bases (search) is trying to derail the process by blocking Senate confirmation of the head of the commission that helps pick which facilities will be shuttered, congressional aides and lobbyists said Thursday.

Most GOP leaders support closing bases and this latest round likely will go forward. But Sen. Trent Lott (search), R-Miss., a staunch defender of military facilities in his state, has pledged to do whatever it takes to block the closures.

Two weeks ago, the Senate Armed Services Committee approved President Bush's nomination of Anthony Principi (search), Bush's former secretary of veterans affairs, to be chairman of the commission overseeing the process.

The full Senate was expected to vote on the nomination last month before lawmakers left for a holiday break.

By May 16, Defense Secretary Donald H. Rumsfeld is supposed to give the commission his list of which military facilities to close in an effort to save money in the Pentagon's annual budget of almost $500 billion.

But Lott has placed a "hold" on the nomination, said aides and lobbyists speaking on condition of anonymity. The procedural move makes it hard for the Senate to vote on it.

They say Lott is expected to try to delay the confirmation of the other eight nominees once the Senate Armed Services Committee approves them.

Calls this week to Lott's office were not returned.

In February, he told The Associated Press, "I will try to stop it at any point and in any way I possibly can." He says the United States should not be closing domestic bases while its troops are waging war abroad.

Principi said he suspects the reason for the delay was not personal, and noted that some lawmakers simply are concerned about the process going forward.

"I happen to know Senator Lott. We happen to get along," Principi said Thursday.

Without confirmation, Principi cannot put together a staff and build an organization meant to give Rumsfeld's list a thorough, independent review.

"It's been a little bit of a delay," Principi said. "We'll just have to move out a little more aggressively."

The Senate committee is expected to take up the nominations of the other eight committee members in the next few weeks.

Lott has lobbied hard during previous rounds to keep open the Meridian Naval Air Station, the Columbus Air Force Base, and Naval Station Pascagoula. All are major employers in his state and all again could be targeted by the Pentagon.

Last year, Lott and Byron Dorgan, D-N.D., proposed delaying the round of domestic base closings until the Pentagon determines what it wants to do with its overseas facilities. The Pentagon and the White House opposed the measure and the Senate defeated it 49-47.