Pentagon officials sought Monday to dissuade a commission from changing any part of Defense Secretary Donald H. Rumsfeld's (search) sweeping proposal to close or downsize military bases (search).

The nine-member panel is considering adding certain bases to his list of recommended closures, a sign that the commission doesn't intend to simply rubber-stamp the proposal, as some in Congress had feared.

The commission sought explanations for why the Pentagon decided to leave open bases including the Marine Corps Recruit Depot in San Diego and the Naval Shipyard at Pearl Harbor, Hawaii.

"While the department stands behind its recommendations, it fully supports the commission's analysis of alternatives," Michael Wynne (search), the Pentagon's technology and weapons-buying chief who oversaw the base project, told commissioners during a Capitol Hill hearing.

However, he stressed that changing one part of the proposal could disrupt other aspects of the "comprehensive, integrated and interdependent" package of recommended changes to the domestic military base structure.

For their part, commissioners expressed reservations over several parts of the proposal, specifically plans to reorganize dozens of Air National Guard bases and close the Portsmouth Naval Shipyard in Kittery, Maine, and move various missions from one base to another.

And, they wanted to know more about the Pentagon's decision to downsize, rather than close, the Naval Air Station in Brunswick, Maine, Pope Air Force Base in North Carolina, and Grand Forks Air Force Base in North Dakota.

The commission is to decide Tuesday whether bases left off the list should be added. Any bases added to the list can be removed later, but the commission won't make those decisions until August.