In an abrupt about-face, the Pentagon has scrapped plans to invoke emergency authority to fast-track construction of a controversial $100 million legal compound at Guantánamo Bay, Cuba.

Instead, Defense Department officials will seek permission from Congress for any new major buildings in which to stage the first war-crimes trials since World War II.

The Pentagon's retreat from a plan it had earlier described as urgent was a setback in Bush administration war-on-terrorism policy, just as the Republican-led Congress finished business Saturday -- to be replaced by a Democratic majority in early January.

California Sen. Dianne Feinstein, a key Democrat on the Senate's military construction and armed services committees, announced the Defense Department's change of course in a news release late Friday -- after members of Congress, both Republicans and Democrats, had protested the move.

''I thank the Department for postponing plans to build a permanent courthouse at Guantánamo Bay,'' Feinstein said. ``It's important this courthouse proceed through regular order, with public hearings, so that there is full knowledge of what is intended.''

Feinstein was among critics of the project, which was first reported by The Miami Herald.

BEHIND THE SCENES

Last month, the Pentagon had quietly notified contractors that it was seeking design and construction bids for the elaborate legal compound -- complete with two courtrooms, housing for 1,200, dining facilities for 800, a 100-vehicle motor pool and conference and other meeting facilities.

A virtual mini military city, the legal compound was projected to cost $75 million to $125 million and be the single-largest construction project at the remote U.S. Navy base in southeast Cuba. Today there are about 420 foreign men and teens held at the base as enemy combatants; about 80 could face war-crimes trials.

The decision to freeze its plan to invoke emergency authority capped a week in which Defense Secretary Donald Rumsfeld said goodbye to Pentagon employees; a blue-chip bipartisan panel said the war in Iraq was mismanaged; and key Republican and Democratic senators introduced legislation to restore captives' rights to challenge their detention -- a move that would give civilian courts a greater role in individual cases at Guantánamo.

The Bush administration has been in a tug of war with civilian attorneys over the rights of the captives at Guantánamo since soon after the prison camp opened in January 2002 with an airlift of 20 captives from Afghanistan. At the time, the Pentagon had provisional plans to house up to 2,000 captives there.

The Pentagon also made the about-face during the same week it put into service a new prison facility -- known as Camp 6. It had cost more than $37 million and was intended as a mediumsecurity prison with communal eating and praying until a riot last summer led to its redesign as a maximum-security compound.

The Miami Herald disclosed the Pentagon's pre-bid solicitation for the legal compound on MiamiHerald.com on Nov. 16.

`EXTREME URGENCY'

The next day, Nov. 17, Deputy Defense Secretary Gordon England wrote Republican and Democratic members of Congress that because of ''national security implications and extreme urgency'' the Pentagon was invoking ''Section 2808 of title 10, United States Code'' as authorization for its fast-track authority -- a move that did not require congressional approval.