WASHINGTON -- The U.S. military's top weapons buyer has approved signing a three-year contract with Lockheed Martin Corp. and United Technologies Corp.'s Pratt & Whitney engine unit for 60 F-22A Raptor warplanes, engines and spare parts, a package worth as much as $10 billion.

Approval of the three-year contract locks the military into purchases and minimizes chances that quantities would be cut in annual congressional budget deliberations.

$65.2 billion program

The Pentagon in 2005 capped the program at 183 aircraft. This contract would complete the $65.2 billion program.

The deal was held up until the Pentagon inspector general reviewed allegations of a potential conflict of interest and a separate study of potential cost savings was completed.

The inspector general in December found there was no conflict of interest.

2nd hurdle cleared

The second hurdle was cleared last week when the Rand Corp. concluded the deal could save as much as $410 million over buying the attack-fighters in separate one-year contracts.

"These savings are substantial and justify the multiyear procurement," wrote Kenneth J. Krieg, the Pentagon's undersecretary for acquisition, to congressional leaders on June 29 in certifying that all conditions have been met for pressing ahead with the contract.

133 engines

The pending deal also includes 133 United Technologies Corp. Pratt & Whitney engines and spare parts.

The Air Force must wait 30 days before signing the contract in case Congress has other concerns, according to legislation that mandated the cost-savings estimate.

Design certified

Krieg certified that the F-22A, which the Air Force declared combat-ready in December 2005, has a "stable design" and that future modifications "are not expected to result in any significant structural changes to the aircraft nor substantial changes" to the Pratt & Whitney engine.

Krieg said "sufficient funding will be available to avoid contract cancellation."

Krieg certified the aircraft "will promote national security" because "there is no alternative aircraft in production offering comparable capabilities. The F-22A is the most advanced fighter in the world."

Lockheed Martin spokesman Rob Fuller said the Bethesda company "was pleased to learn" of the new cost-savings estimates. The contract will cover production through 2011, Fuller said.

The aircraft are assembled at Lockheed Martin's plant in Marietta, Ga.