The Army official who managed the Pentagon's largest contract in Iraq says he was ousted from his job when he refused to approve paying more than $1 billion in questionable charges to KBR, the Houston-based company that has provided food, housing and other services to American troops.

The official, Charles M. Smith, was the senior civilian overseeing the multibillion-dollar contract with KBR during the first two years of the war. Speaking out for the first time, Mr. Smith said that he was forced from his job in 2004 after informing KBR officials that the Army would impose escalating financial penalties if they failed to improve their chaotic Iraqi operations.

Army auditors had determined that KBR lacked credible data or records for more than $1 billion in spending, so Mr. Smith refused to sign off on the payments to the company. "They had a gigantic amount of costs they couldn't justify," he said in an interview. "Ultimately, the money that was going to KBR was money being taken away from the troops, and I wasn't going to do that."