The commander of U.S. Central Command said as much to Congress last week, and a new report from the Government Accountability Office highlighted the problem.

"I couldn't give you an accurate figure on that, sir," said. Adm. William Fallon, the new commander of CENTCOM. "I know that we have a lot of people. I've seen a lot of Americans. I have no idea how many are actually there."

The U.S. Army has begun compiling a database of contractors that currently numbers 50,000, but not all of those at work in the wars have been accounted for.

GAO reiterated its warning in a report released Monday that the U.S. military's failure to stringently oversee the billions in dollars spent in Iraq on private contractors -- whose duties range from acting as bodyguards and gate guards to vehicle maintenance, cleaning bathrooms and doing laundry -- makes well-funded war coffers ripe for fraud, waste and abuse.

For instance, according to the GAO, the Army loses $43 million a year providing free meals to contractors who also receive a per diem -- charged to the government -- for food.

It's a problem that predates the Iraq war. Contractors began to be heavily relied on for tasks formerly performed by the military in the 1990s -- after the major drawdown of forces that followed the collapse of the Soviet Union.

But the U.S. Department of Defense still lacks clear and comprehensive guidance and leadership for managing and overseeing contractors. It is also short of people trained to oversee the complicated contracts, both in the United States and in the war zone.