WASHINGTON — The weight of the war has proven to be too heavy for a growing number of soldiers.

Faced with difficult and repeated tours in Afghanistan and Iraq, deployments that stretch for 15 months, and signs of lingering stress disorders, more soldiers are finding a way out: desertion.

According to the Army, soldiers are deserting their posts at the highest rate since 1980, with the number of Army deserters this year showing an 80 percent increase since the U.S. invaded Iraq in 2003.

While the totals are still far lower than during the Vietnam War, when the draft was in effect, they show a steady increase over the past four years and a 42 percent jump since last year.

"We're asking a lot of soldiers these days," said Roy Wallace, director of plans and resources for Army personnel. "They're humans. They have all sorts of issues back home ... So I'm sure it has to do with the stress of being a soldier."

The Army defines a deserter as someone who has been absent without leave for longer than 30 days. The soldier is then discharged as a deserter.

According to the Army, about nine in every 1,000 soldiers deserted in fiscal 2007, which ended Sept. 30, compared with nearly seven per 1,000 a year earlier. Overall, 4,698 soldiers deserted this year, compared with 3,301 last year.

The increase comes as the Army continues to bear the brunt of the war demands, with many soldiers serving repeated long tours in Iraq and Afghanistan. Military leaders — including Army chief of staff Gen. George Casey — have acknowledged that the Army has been stretched nearly to the breaking point. Efforts are under way to increase the size of the Army and Marine Corps to give troops more time off between deployments.

"The Army can't afford to throw away good people," Wallace said. "We have got to work with those individuals and try to help them become good soldiers."