In a largely invisible cost of the war in Iraq, nearly 800 civilians working under contract to the Pentagon have been killed and more than 3,300 hurt doing jobs normally handled by the U.S. military, according to figures gathered by The Associated Press.

Exactly how many of these employees doing the Pentagon's work are Americans is uncertain. But the casualty figures make it clear that the Defense Department's count of more than 3,100 U.S. military dead does not tell the whole story.

“It's another unseen expense of the war,” said Thomas Houle, a retired Air Force reservist whose brother-in-law died while driving a truck in Iraq. “It's almost disrespectful that it doesn't get the kind of publicity or respect that a soldier would.”

Employees of defense contractors such as Halliburton, Blackwater and Wackenhut cook meals, do laundry, repair infrastruture, translate documents, analyze intelligence, guard prisoners, protect military convoys, deliver water in the heavily fortified Green Zone and stand sentry at buildings - often highly dangerous duties almost identical to those performed by many U.S. troops.

The U.S. has outsourced so many war and reconstruction duties that there are almost as many contractors (120,000) as U.S. troops (135,000) in the war zone.

The insurgents in Iraq make little if any distinction between the contractors and U.S. troops.

In January, four contractors for Blackwater were killed when their helicopter was downed by gunfire in Baghdad. In 2004, two Americans and a British engineer were kidnapped and decapitated. That same year, a mob of insurgents ambushed a supply convoy escorted by contractors, burning and mutilating the guards' bodies and stringing up two of them from a bridge.

But when contractors are killed or wounded, the casualties are off the books, in a sense.

While the Defense Department issues a press release whenever a soldier or Marine dies, the AP had to file a Freedom of Information Act request to obtain figures on pre-2006 civilian deaths and injuries from the Labor Department, which tracks workers' compensation claims.

By the end of 2006, the Labor Department had quietly recorded 769 deaths and 3,367 injuries serious enough to require four or more days off the job.

“It used to be, womb to tomb, the military took care of everything. We had cooks. We had people who ran recreation facilities. But those are not core competencies you need to run a war,” said Brig. Gen. Neil Dial, deputy director of intelligence for U.S. Central Command.

With the all-volunteer force, the military began more stringent recruiting of troops and made greater use of nonmilitary professionals. “It puts professionals in harm's way,” he conceded.

Although contractors were widely used in Vietnam for support and reconstruction tasks, they have never before represented such a large portion of the U.S. presence in a war zone or accounted for so many security and military-like jobs, experts say.

Some of the workers are former U.S. military personnel. Some are foreigners. The companies and the U.S. government say they do not keep track of how many are Americans.

The contractors are paid handsomely for the risks they take, with some making $100,000 or more per year, mostly tax-free - at least six times more than a new Army private, a rank likely to be driving a truck or doing some other unskilled work.

The difference in pay can create ill will between the contractors and U.S. troops.

“When they are side by side doing the same job, there is some resentment,” said Rick Saccone, who worked as an intelligence contractor in Baghdad for a year.

If the contractor deaths were added to the Pentagon's count of U.S. military casualties, the number of war dead would climb about 25 percent, from about 3,000 as of the end of 2006 to nearly 3,800.

If the contractors injured badly enough to be off the job for at least four days were added to the nearly 14,000 U.S. troops requiring medical air transport because of injuries, the injury total would rise by about the same percentage.

Early in the war, most of the casualties on the coalition side were military. But with the fall of Saddam Hussein, contractors flowed in behind the troops, and the number of deaths among the contract workers has been increasing each year.

Contractor deaths are less costly politically, said Deborah Avant, a political science professor at George Washington University.

“Every time there's a new thing that the U.S. government wants the military to do and there's not enough military to do it, contractors are hired,” she said. “When we see the 3,000 service member deaths, there's probably an additional 1,000 deaths we don't see.”

Houle's brother-in-law, Hector C. Patino, was driving a truck for a Halliburton subsidiary in the Green Zone when he was killed by friendly fire at an Australian checkpoint.

Patino, who served two tours in Vietnam, thought he was safe, said his mother, 82-year-old Flora Patino.

“I said, ‘Hector, you're playing with fire,'” she recalled.

- Associated Press writer Elizabeth White in San Antonio and Randy Herschaft in New York contributed to this report.