The FBI plans to spend up to $500 million building the final piece of its delayed, troubled technology upgrade, yet risks a repeat of earlier missteps that led to excessive costs, according to a government report released Monday.

Still, the bureau apparently has learned several lessons from its last, failed attempt to give agents and analysts a computerized case management system, the $170 million Virtual Case File, Justice Department Inspector General Glenn A. Fine said in the report.

FBI Director Robert Mueller III scrapped VCF last year, after consultants said it was obsolete and riddled with problems, and said a more flexible, phased program -- dubbed Sentinel -- would take its place.

The FBI said late last week that it intends to award the first contract for Sentinel within 30 days and is in final talks with one of the two bidders for the work. The FBI declined to identify the bidder, but a government official who has been briefed on the negotiations said it is Lockheed Martin Corp. He spoke on condition of anonymity because the negotiations are continuing.

The bureau also has refused to state the anticipated cost of Sentinel, saying it would hamper negotiations with bidders, and would not give a detailed estimate to Fine's team of auditors. But the inspector general said the FBI had told a Senate committee late last year that it would cost $400 to $500 to build Sentinel.

While "the FBI has taken important steps to help prevent the types of problems encountered in the Virtual Case File project," Fine said the bureau has not yet put in place a system to track and control costs in the new project .

"We view the potential weaknesses in cost control over the Sentinel project as a significant project risk," he said.

Zalmai Azmi, the FBI's chief information officer, said in response to the audit that the FBI has taken steps to keep costs in check.