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. But he was suddenly replaced, he said, and his successors - after taking the unusual step of hiring an outside contractor to consider KBR's claims - approved most of the payments he had tried to block. Mr. Smith's account fills in important gaps about the Pentagon's handling of the KBR contract, which has cost more than $20 billion so far and has come under fierce criticism from lawmakers. Mr. Smith ... is giving his account just as the Pentagon has recently awarded KBR part of a 10-year, $150 billion contract in Iraq.