The United States is considering cutting and reconfiguring U.S. forces in Europe and South Korea as part of a broader effort to restructure the military for 21st century threats.

Pentagon officials said Tuesday that no firm plans are in place, but serious thought has been given to reducing the size of the force in Germany, the traditional focal point of the U.S. presence in Europe.

The intent would be to make the American force, now numbering about 71,000 troops - three-quarters of them Army soldiers - more flexible by rotating it regularly and drastically reducing the permanent base structures that support the troops, Army and other officials said.

The officials said these potential changes are not related directly to the rift that has developed in recent weeks between the United States and Germany over Iraq policy. The changes reflect the administration's effort to shed the military of Cold War-era structures and practices.

Richard Perle, chairman of a group that advises Defense Secretary Donald H. Rumsfeld on policy issues, told reporters Wednesday that "operational efficiency" ought to be the guiding principle.

"We should not and would not change our base structure in some fit of pique," Perle said.

In testimony on Capitol Hill, Army Secretary Thomas White and Gen. Eric Shinseki, the Army chief of staff, said decisions on revamping the Army's structure in Europe would be made only after the Iraq crisis is settled.

White said he believed a restructuring would mean shifting some soldiers to bases elsewhere in the world, rather than reducing the overall size of the Army. Shinseki said he is still trying to persuade Rumsfeld that the Army, which numbers 480,000 soldiers, needs to get bigger.

The Pentagon also is contemplating major changes in its troop presence in South Korea, where American troops have served as a deterrent to North Korea since the end of the Korean War in 1953.

Without publicly announcing it, the United States and South Korea in recent weeks agreed to explore ways of accelerating and expanding an agreement reached last year to reduce the number of U.S. troop installations in South Korea from 41 to 25 over the next 10 years, a senior official said.

No commitment has been made yet to reduce the number of U.S. troops in South Korea, but that is an implied consequence of the kinds of changes being contemplated.

The official, who discussed the matter on condition of anonymity, said the Pentagon is looking for ways of "trading troop strength for capability," a reference to reducing the number of U.S. troops while changing their structure in order not to lose combat strength.

About 37,000 U.S. troops currently are posted in South Korea.

South Korea's President-elect Roh Moo-hyun has made clear to the Bush administration that he does not want a complete withdrawal of American forces but seeks to "rebalance" the U.S.-South Korean alliance, the U.S. official said. The official said it could take six to 12 months to sort this out.

Ari Fleischer, the White House spokesman, was asked Tuesday whether the president would consider cutting U.S. forces in South Korea or Germany.

"Eleven years after the end of the Cold War, there is a school of thought to rethink the numbers and types of forces we have in different locations as events warrant," Fleischer said. He said the goal would be to maintain a military presence "to assure our friends and allies."

Maj. Tim Blair, a Pentagon spokesman, said "there is no plan on paper" for changes in Europe.

Other officials, however, said interest is high in transforming the U.S. force in Germany into a lighter, more mobile force capable of moving on short notice to hot spots elsewhere.

The New York Times and The Washington Post reported Monday that members of Congress were briefed on the subject last week by Marine Corps Gen. James Jones, the new commander of the U.S. European Command. They said he presented his preliminary thoughts, not a final plan.

Rep. Duncan Hunter, R-Calif. said Tuesday the House Armed Services Committee will hold a hearing this month on whether U.S. forces in Europe should be restructured. He is committee chairman.

Sen. John Warner, R-Va., chairman of the Senate Armed Services Committee, agreed Tuesday that change is needed in Germany.

"It's been long in coming," he said. Change, he said, is "not only inevitable, it's essential."