Washington ? The administration’s talk about sharply reducing the number of American troops in Iraq starting as early as next spring gets a strong endorsement from military experts, both those who support the war and those who question it.

But they also say there is much more to the “trial balloon” floated by U.S. officials last week than the situation on the ground, which Gen. George W. Casey, commander of American forces in Iraq, says is stable enough to draw down the troop level.

One key factor cited from across the political spectrum is the mounting strain on the U.S. military, particularly the Army, Marines, National Guard and Reserves, whose members are facing multiple deployments to Iraq.

Lawrence Korb, former assistant secretary of defense in the Reagan administration and now the military expert at the Center for American Progress, agrees the administration has no choice because of the effect on American soldiers. Problems the military is already having recruiting new soldiers will turn into problems of retaining current ones, he said.

“If they don’t withdraw them in a year, or draw back significantly, they break the Army,” Korb said. “They know that.”

At the same time, the administration’s hand also is being forced by other factors, experts say, including:

l A need to signal to Iraqi officials that they cannot rely indefinitely on American forces to provide security, and must speed up formation of a permanent government and development of their own military and police forces.

l Hopes of showing the Iraqi public, including those disaffected by the American presence, that the United States has no long-term designs on their country, contrary to the claims of insurgents.

l The desire to reassure the American public, whose support for the war is flagging according to polls, that progress is being made, allowing the government to begin the orderly withdrawal of U.S. troops.

Michael O’Hanlon, military expert at the Brookings Institution, says the administration is smart to send a signal to Iraqis.

“I think it helps with the politics of the whole thing, helps to defuse the idea that we are an occupying force, that we want to control the oil and use Iraq as a springboard for other regional activity,” he said. “That has been a major motivation for the insurgency.”