Blackwater Chief Defends Firm

He said contractors follow a strict protocol for "escalation of force" against Iraqis who appear to be threatening a convoy, first using "hand signals and audible yelling," and then firing flares. "Water bottles are sometimes thrown at vehicles to warn them off. If you have to go beyond that, they take shots, hitting the radiator," followed by shots to the windshield.

"Only after that," Prince said, "do they actually direct any shots toward the driver."

In one case reported by the committee, Prince said, an Iraqi bystander was hit by a ricocheting bullet fired by a Blackwater guard.

After Prince's four-hour appearance, Griffin and two other State Department officials defended the use of private security contractors on the grounds that the firms offered the fastest way to provide protective services and fill what was originally expected to be a short-term need.

Saying that he had "personally benefited from Blackwater and other private security details" while serving in Iraq from 2005 to 2006, David M. Satterfield, the State Department's coordinator for Iraq, said that U.S. diplomats there would not be able to function without them.

"We believe [private security contractors] have performed exceedingly well, with professionalism and with courage," he said.

Democrats challenged the department's oversight of the security contractors and suggested that the work could be done by the government or the military at a much lower cost. "The taxpayers are not getting their money's worth," Waxman said, and he and others said that complaints about contractors' recklessness are hurting the U.S. war effort.

Prince disputed the assertion that the contractors make much more money than U.S. soldiers in Iraq. He said contracts worth hundreds of millions of dollars for work there do not reflect company expenditures on everything from body armor to helicopters.

"If the government doesn't want us to do this," he said, "we'll go do something else."