The US government has no precise figure for how many contractors are employed in Iraq and Afghanistan, inviting the risk of fraud and security threats, a US commission warned on Monday.

"It is both peculiar and troubling that eight years after the overthrow of the Taliban regime, in Afghanistan, and more than six years since the overthrow of Baathist regime in Iraq, we still don't know how many contractor employees are working in the region," said Michael Thibault, co-chairman of the commission on wartime contracting.

The independent commission found that "there is no single source for a clear, complete and accurate picture of contractor numbers, locations, contracts and cost," Thibault said at a commission hearing.

"How can contractors be properly managed if we aren't sure how many there are, where they are and what are they doing?"

The Pentagon had a data base for contractors but it did not take into account the large number of foreign nationals performing contract work, while a data base kept by US Central Command did not count employees with the State Department, he said.

The Pentagon in April counted about 160,000 contractors mainly in Iraq, Afghanistan and Kuwait but Central Command recorded more than 242,000 contractors a month earlier, he said.

The lack of precise numbers for contractors "permits and invites waste, fraud and abuse of taxpayer money and undermines the achievement of US mission objectives," he said.

The problem also raises concerns over security, he said.

Although most contractors were doing valuable work, often at personal risk, Thibault said "it takes only one foreign national contractor employee smuggling explosives into a dining facility, headquarters, hospital or barracks to create a mass casualty disaster," he said.

The bipartisan commission on wartime contracting was created last year by Congress to examine government contracting for reconstruction, logistics and security operations and to recommend reforms.