Army officials announced yesterday that thousands of active-duty and reserve soldiers who are nearing the end of their volunteer service commitments could be forced to serve an entire tour overseas if their units are chosen for deployment to Iraq or Afghanistan.

The order applies to all Army soldiers who are deployed in the future and means that many troops could face extended terms in the military after their formal contracts expire. The Army had previously issued such orders on a unit-by-unit basis, as troops deployed. Now, all soldiers are on notice that if their units are called into the fight, they will go -- and stay.

Soldiers will be notified 90 days before their units are to deploy, and by policy, all soldiers must then serve with their units until 90 days after they return. If a soldier's scheduled service end date falls within that window, he or she will be forced to serve the entire tour.

Army officials said the move promotes cohesion by preventing Army divisions from being depleted shortly before they go into battle. But military experts and lawmakers said the decision indicates that the Army is being stretched thin by multiple operations, with some calling the program a draft in disguise.

"It's a blanket imposition of extended service, and it has to raise questions about how adequately manned the Army is," said Loren Thompson of the Lexington Institute, a nonpartisan think tank.

The "stop-loss" policy prevents the normal attrition of troops and ensures that divisions will not have to seek additional troops when they go to Iraq or Afghanistan, said Lt. Gen. Franklin L. Hagenbeck, the Army's deputy chief of staff in charge of human resources and personnel. Congress authorized such measures after the Vietnam War, and they were first used during preparations for the Persian Gulf War in 1990. They have been used since to bolster divisions heading to Iraq and Afghanistan.

"If we don't do that, a division would change 4,000 people out just before deployment, and that's nonsensical," Hagenbeck said yesterday. He said it "puts soldiers' lives at risk" to have soldiers meeting for the first time on the battlefield.

All 160,000 U.S. troops in Iraq, Afghanistan, Kuwait and Qatar are serving under the same stop-loss conditions, but Army officials decided to announce a policy that alerts all troops for the future. Though Hagenbeck said the Army does not need more troops, he acknowledged that it is "stretched."

Because the U.S. military intends to keep about 140,000 troops in Iraq through 2005 to fend off an insurgency -- instead of scaling down significantly, as originally planned -- officials have extended the tours of 20,000 troops and recently announced that they will draw more than 3,500 troops from South Korea to support the mission. A few units are scheduled to deploy this summer to relieve the extended troops, and a full-scale rotation of troops is scheduled for this fall.

John Tillson, an expert with the Institute for Defense Analysis, said he thinks the stop-loss policy is essential to maintaining a presence around the globe. "We're in a war, so the question is, who pays the burden?" he said. "The people who pay the burden are those who volunteered to join the military."

Some, however, do not see that as fair. One Army brigade commander, speaking on the condition of anonymity, said: "A soldier just said to me, 'What happened to the volunteer force? This is a draft.' "

Members of Congress have been calling for a permanent increase in the Army's size to deal with the war on terrorism, but the Pentagon has resisted that amid a call for a lighter, more mobile military. Sen. Jack Reed (D-R.I.), a member of the Armed Services Committee, yesterday renewed his call to permanently enlarge the Army by 20,000 soldiers.

For Jessica Salamon of Ravenna, Ohio, the stop-loss policy has already affected her and her husband, Chad, a National Guardsman who is serving in Iraq with the 118th Medical Battalion as a mechanic. Chad Salamon's six-year commitment should end in March, but he is almost certain not to return by then.

"This is supposed to be an all-volunteer military," said Jessica Salamon, who has been to therapy and has seen her dream of starting a family deferred. "They're not volunteering when they're told they can't leave."

In a presidential campaign speech in Tampa, Sen. John F. Kerry (D-Mass.) said the military should not force soldiers to fight.

"You have what is a backdoor draft that has been put into effect," Kerry said. "People serving beyond the time of their voluntary service are no longer volunteers."

Staff writer Thomas E. Ricks contributed to this report.

A soldier secures the scene of a car-bomb explosion that killed at least four and injured 20 north of Baghdad. The new policy will affect both active-duty soldiers and reservists.