The U.S. Air Force affirmed on Thursday its plans to buy 1,763 F-35 fighter jets built by Lockheed Martin Corp in coming years, as Lockheed and the government neared agreement on a multi-billion dollar contract for a fifth batch of planes.

Air Force Secretary Michael Donley told an investor conference that the service remained committed to the F-35 Joint Strike Fighter, which alone accounts for 15 percent of the service’s annual investment spending, and had no plans to revise its projected purchase of 1,763 of the new radar-evading jets.

“I don’t think there’s any reason to revisit that anytime in the near future,” Donley told the Credit Suisse conference, underscoring his support for the Pentagon’s biggest weapons program.

He said it was not feasible to consider cutting orders or make other major changes to the $396 billion F-35 program, which has already been restructured three times in recent years to allow more time for technology development and to save money.

The Pentagon is looking closely at every aspect of its budget given mounting pressure to cut defense spending, and programs as large as the F-35 are always potential targets.

But Lockheed executives argue that the Defense Department has already reduced production of the new plane sharply from projected levels, cutting into the economies of scale that were supposed to make the new warplane more affordable.

Donley said he had heard proposals about cutting F-35 purchases to save money for other priorities, but said such ideas did not make sense at this point in the program.

“These are good theoretical discussions, but when you look at where we are in the program, it makes no sense to have these discussions until about 2025,” Donley said. “There is nothing in the near-term about this program that will change; there is nothing that it will contribute to deficit reduction in the next ten years with the exception of its cancellation.”