The Army plans to shore up its ability to reinforce troops in the Middle East by freezing the release of officers and enlisted personnel from all units, Army officials said last night.

The move would force tens of thousands of Army personnel to remain in uniform at least temporarily despite their desire to leave the service, officials said.

The action would halt voluntary retirement from service, trim vacations for trainees, end transfers unrelated to the Persian Gulf crisis and hold in the Army troops whose skills could be crucial to the U.S. effort in the gulf, officials said.

"With 40 percent of our forces over there in the gulf," said one Army leader, "we want to make sure that we keep stability in the units in the continental United States in case they are needed to reinforce the Persian Gulf deployment."

Some experts on troop strength have expressed concern that the Army will not have enough combat-ready replacements for those who would be killed or wounded in a gulf war unless the release of officers and enlisted personnel is halted.

An Army official said the planned freeze would be an expansion of an earlier order, which applied only to soldiers stationed in the gulf, freezing voluntary retirements. Each year, voluntary retirements typically involve 10 percent of the Army officer corps of 104,735 personnel and 20 percent of the 625,517 enlisted personnel. The official said the expanded order would affect virtually the whole Army, allowing for a screening period in which leaders would determine soldiers who may be needed for future deployment and those who can safely be released.

The Air Force and Navy also are considering expanding their freeze authority to cover units outside the gulf, defense officials said. There have been discussions about doing this for the Marine Corps as well, but no decisions have been made, they said.

"We've got to have the ability to reinforce," said one Army official in explaining the proposed freeze. Although the order has not yet been implemented, officials said it is expected to take effect on Dec. 1. The order means, one official said, that "you're on hold until further notice."

Details of the plan are still being worked out, and limited exemptions to the order are expected to be granted for "hardship cases" such as family medical troubles, a Defense Department official said.

He said the purpose of the freeze is "to ensure that the Army is able to maintain worldwide readiness" and to help support Operation Desert Shield, the Middle East deployment of more than 230,000 U.S. troops in response to Iraq's Aug. 2 invasion of Kuwait.

An estimated 120,000 Army troops are now deployed in Saudi Arabia under the operation, and officials have estimated that another 75,000 to 100,000 soldiers will be sent there over the next two months under a decision announced by Defense Secretary Richard B. Cheney two weeks ago.

The freeze authority was granted to the Defense Department, and indirectly to the military services, under a little-noticed executive order signed by President Bush on Aug. 22.

It formally authorizes a suspension "of any provision of law relating to promotion, retirement or separation applicable to any member of the armed forces determined to be essential to the national security of the United States."

So-called "mandatory retirements," given to personnel passed over for promotion, will still occur under the new order.

An Army official said she was uncertain whether enlistees were aware that they could be forced to remain in service longer than they desired. "Does every soldier know the details of the U.S. Code Title 10 {the legal authority for the president's action}? Probably not," she said.

The Army decision is the latest in a series of efforts by the military services to respond to the extraordinary demands of Operation Desert Shield. Earlier this week, the Army called 20,129 more reservists to active duty. The Navy called up 875 reserve sailors, and the Marines called 6,496. Since the invasion, Cheney has authorized activation of up to 125,000 reservists from all three services so the United States could deploy nearly 400,000 troops at bases in Saudi Arabia and on nearby naval vessels.