Lockheed Martin Corp on Wednesday said it was continuing work to sharply reduce the costs of the F-35 fighter and did not believe the program was in trouble despite a report that the Pentagon will cut production of 122 airplanes through 2015.

Lockheed spokesman Chris Geisel said the company was running about four to six months late on finishing the final four of 19 developmental aircraft, which in turn prevented completion of all the flight tests planned by the end of 2009.

He said the gap was narrowing between Pentagon and Lockheed projections about the cost and time required to complete the development program.

Senior Lockheed officials were meeting this week with top Pentagon officials to hammer out a final plan for funding the program in fiscal 2011 and the coming years, Geisel said.

Much of the information that's recently been reported is pre-decisional and we continue to work with the (Office of the Secretary of Defense) to come to resolution, he said.

He said the possible changes being discussed would not affect the U.S. government's plan to buy a total 2,443 F-35s for the three military services, or the dates that the services have set for starting to use the new fighter jets.

The program is not in trouble. We are a little behind on delivery of the (system design and development) aircraft, about six months, but the rest of the aircraft will be delivered within the next four to six months.

Bloomberg on Wednesday reported that Defense Secretary Robert Gates directed the military in a December 23 budget memorandum to delay the F-35 program, cutting planned purchases by 10 aircraft in fiscal 2011 and a total of 122 through 2015.

Gates cut the planned purchase of F-35s by 10 planes in 2011 to 42; by 17 in 2012 to 45; by 52 in 2013 to 77; by 20 in 2014 to 90; and 23 in 2015 to 107, Bloomberg said, citing the document.

No comment was immediately available from the Pentagon's F-35 office.

It said the Pentagon would use more than $2.8 billion that was budgeted earlier to buy the military's next-generation fighter would instead be used to continue its development.

If the plan is approved the money would be used to complete flight testing more quickly and work on other issues, such as software development, said one source familiar with the issue, who was not authorized to speak publicly.

But he said that the Pentagon could potentially add back in the production airplanes if Lockheed and the program were able to beat their cost and schedule targets.

(Reporting by Andrea Shalal-Esa; editing by Carol Bishopric)