Defense Secretary Donald H. Rumsfeld (search) on Monday defended his recommendation to close 33 major domestic bases and to shut or consolidate hundreds of smaller installations, calling the sweeping realignment essential in a time of war.

"Those changes are more necessary, not less, during" wartime, Rumsfeld said as a nine-member congressionally chartered commission opened hearings into the base-closing plan that will go to President Bush this fall and then to Congress.

In past base closure rounds, the commission has gone along with about 85 percent of what the Pentagon recommended.

The current panel sounded receptive to what Rumsfeld had proposed, with some misgivings about the changes targeting National Guard (search) and reserve units -- a distressing omen to affected communities counting on the commission to spare their facility.

Once the commission sends its plan to the president, it must be accepted or rejected in its entirety by both President Bush and Congress.

The Pentagon plan would close 33 major domestic bases and to shut or consolidate hundreds of smaller installations.

"The department is in need of change and adjustment," Rumsfeld told the base-closing commission. "The current arrangement, designed for the Cold War, must give way to new demands of the war against extremism and other evolving challenges in the world."

Remarks and pointed questions by members of the panel underscored the difficulties ahead for what commission chairman Anthony Principi (search) called an "arduous task and assessment."

"If your proposals are accepted, they will have profound effects on the communities and people who bring them to life," Principi, a former Veterans Affairs secretary, said.

Former Utah congressman James V. Hansen, a Republican, told Rumsfeld he was certain this would be the last round of closures in the face of swelling political opposition.

"I'm convinced this is your last bite of the apple," Hansen said, saying the plan would bring "a lot of pain for a lot of people."

"Certainly, it's the last bite of the apple during my watch," Rumsfeld answered. But, citing the always-changing needs of the military, the defense secretary added: "I would think it may happen again."

Rumsfeld said he agreed that the chore "undoubtedly will be a formidable task."

The plan was the fifth round of base closings. The last one was in 1995.

The panel will hold hearings around the country.

Rumsfeld is proposing to close and shrink hundreds of bases to create a leaner, more cost-effective force. If accepted, the plan would alter the domestic military landscape and greatly affect the four service branches and communities that are home to the installations.

Rumsfeld appeared with Gen. Richard Myers, chairman of the Joint Chiefs of Staff (search).

"If we don't make some of this happen, we're going to be stuck in the cold war mind set for a long time to come," Myers told the panel.

Said Rumsfeld: "Some asked why we're proposing any base closures during a time of war. The answer is the changes are essential in helping us win this conflict."

By closing and consolidating facilities it no longer requires, the Pentagon says it would save about $49 billion over the next 20 years for the additional personnel and equipment it needs.

Rumsfeld said that he didn't personally change any of the recommendations that came to his desk from the different military services and the Pentagon officials in charge of drafting the recommendations.

The defense secretary said he understood the changes would bring pain to many communities. But, he said, overall the plan would "help move forces and resources to where they can best provide for our nation's defense."

During questioning, a Democratic member of the panel, former Rep. James H. Bilbray of Nevada, noted that "four-fifths of the closures are Guard and Reserve centers" and asked what the impact might be on a war in Iraq that "drags on."

"None of these units go away," Myers said, saying that the centers would just be performing a different role.

Rumsfeld defended the recommendation to close the venerable Walter Reed hospital (search) in Washington and to shift staff and services to the Navy's national medical center in nearby Bethesda, Md.

"Bringing service members together under one umbrella" would improve the military's ability to serve its wounded and their families, Rumsfeld said.

In all, the Pentagon proposed closing or reducing forces at 62 major bases and 775 minor installations. Dozens of other facilities would grow, absorbing troops from domestic and overseas U.S. bases slated for closure or downsizing.