The Pentagon announced yesterday that it is considering a call-up of Army combat reserve units but, in a tacit admission that those units may not be ready to fight in the Persian Gulf, Pentagon spokesman Pete Williams said the reserves would likely go to training camp in the American desert first.

"The decision may well be to put them out in the desert and see how they do before any decision is made on whether to deploy them or not," Williams told reporters. "You don't want to send anyone there until you have full faith and confidence in a tested environment in their ability to defend themselves . . . "

Defense Secretary Richard B. Cheney this week initiated the first combat reserve call-up since the Korean War when the Marine Corps asked for and received his permission to summon 3,000 Marine reservists to fill out the 5th Marine Expeditionary Brigade, which would probably be sent to the gulf under a rotation plan now in its final draft.

The first 824 Marines are being called up this week from units in 14 states, and will report to Camp Pendleton, Calif. Among those called up were 189 members of the 4th Assault Amphibious Battalion, Company A, the majority of whom are based in Norfolk, and up to 40 reservists assigned to the 4th Combat Engineer Battalion in Baltimore.

If they go to the Persian Gulf, they will join the more than 200,000 U.S. combat troops and 34,000 non-combat reservists from all services who already are working in support roles in Saudi Arabia as drivers, stevedores, cooks, laundry workers and water purifiers.

Williams said Cheney may grant similar call-up authority to the Army to summon the "round out" combat reserve brigades for the major Army units now deployed.

Speculation about a large call-up of the Army combat reserves intensified in recent days after Cheney said publicly that an additional 100,000 U.S. troops might soon be deployed to the Middle East.

But an Army official said yesterday that a new Army reserve call-up would likely be substantially smaller than the call-up of non-combat reservists initiated in August. This reflects a keen sensitivity in the Bush administration that a broad military call-up of civilians for a year of desert service could quickly generate political dissent at home, Pentagon officials said.

The bulk of any additional forces going to the Persian Gulf in coming months is expected to come from Europe, where 50,000 U.S. troops are standing by for reassignment, and from active duty divisions in the United States. The decision-making timetable for these new force deployments has been slowed by complex manpower planning in the Army and the Joint Chiefs of Staff, officials said.

Under the Pentagon's "total force" policy, the Army keeps part of its fighting forces in the Army Reserve and state national guard units as a way to save on manpower costs in the active Army.

Combat reservists train with their units once a month and spend two weeks each summer in more extensive weapons and tactical training.

In wartime, the total force policy holds that these Army reservists are to join the active duty brigades immediately to "round out" each division designated for combat as part of the "surge" capability of the U.S. armed forces.

Sen. Sam Nunn (D-Ga.) and Rep. Les Aspin (D-Wis.), who chair the Senate and House armed services committees, have pressed for such a reserve strategy and, since the Aug. 2 Iraqi invasion of Kuwait, have publicly questioned why the Pentagon has thus far failed to integrate the combat reserve forces in the U.S. deployment.

The Pentagon's answer has been that the 90-day call-up authority authorized by Congress made it impractical to put the Army combat reserves into play for such a short time. Congress, in legislation President Bush signed Monday night, doubled the call-up period to 180 days, which can be doubled again with congressional notification.