Chicago ? Boeing Co. said Friday it was reducing efforts to convert its 767 planes for use as Air Force refueling tankers as a result of government reviews into the controversial program — a move that would result in as many as 150 job cuts at its plants in Wichita and Seattle.

CEO Harry Stonecipher said 600 Boeing employees at those locations would be shifted to other work as the company slows development on a delayed Air Force project that has been costing it about $1 million a day.

“Because important and detailed day-to-day dialogue with our customer is necessary to refine program requirements, we do not believe that continuing development work at the current level of effort is prudent for either the Air Force or Boeing,” Stonecipher said.

The cutback comes after the Pentagon ordered three additional reviews into Boeing’s plan to lease and sell 100 jets to the Air Force for use as refueling tankers.

The Defense Department said earlier this month that the Air Force can’t proceed with the contract — already suspended since early December pending an investigation — until reviews by the Pentagon general counsel, the Defense Science Board and the Industrial College of the Armed Forces are completed.

Those reviews are expected to take at least until May, according to the Defense Department.

The Pentagon’s inspector general already had been looking into the case after questions arose last year about ethical issues surrounding the way Boeing pursued the multibillion-dollar contract.

Stonecipher said development efforts on the project would be slowed starting Monday, with key program elements kept intact while the federal reviews proceed. He cited the $270 million Boeing already spent on the tanker program through the end of 2003, not counting the million-dollar-a-day cost through 50 days of 2004.

About 100 contract employees in Wichita will be let go and up to 50 employees in Puget Sound, Wash., will be laid off, he said.

“We deeply regret the difficulties that this slowdown will pose for our Boeing employees and those of our teammates,” Stonecipher said.

Dick Ziegler, a spokesman for Boeing in Wichita, said the 100 contract engineers Boeing released come from various companies working on the tanker modification program.

In an unrelated move, Boeing also issued 38 layoff notices Friday to Boeing employees in Wichita, Ziegler said. The 60-day notices are effective April 23. Friday also was the last day of work for 18 Boeing workers who had received earlier notices.

The tanker deal is considered crucial to keeping Boeing’s slumping 767 production line alive. Merrill Lynch analyst Byron Callan said in a research report earlier Friday that if the tanker deal remains in limbo by early summer, Boeing likely will move to end production of the 767.

“This could be a close call,” Callan said.

Boeing shares lost 18 cents to close at $44.34 on the New York Stock Exchange.