The Pentagon will buy fewer F-35s than planned if program costs keep rising, says a senior U.S. defense official.

“If there is [additional] cost growth, then we will have to reduce the buy,” Robert Hale, Pentagon comptroller, said Wednesday during a Precision Strike Association-sponsored conference in Arlington, Va. “I don’t see us getting additional funding” above the $708 billion in the Obama administration’s 2011 defense spending proposal.

The Air Force, Navy and Marine Corps are set to buy more than 2,400 Lockheed Martin F-35s. The Air Force will buy a conventional take-off-and-landing variant, while the Navy will buy a carrier version, and the Marines will purchase a short-takeoff-and-landing variant.

In addition, eight other nations are officially signed on to buy the Lightning II war jet. Singapore and Israel are also expected to buy it. Sources say the Pentagon is pushing Japan to purchase some number of F-35s.

The three U.S. services currently plan to buy a bit more than 2,400 F-35s. Eight other nations are partners on the fifth-generation fighter effort. Two more, Israel and Singapore, could buy the jet, too.

Hale spoke one day before Pentagon acquisition chief Ashton Carter is to jet to Texas to brief the procurement chiefs of the program’s international partners on DoD’s F-35 restructuring. Also expected to be a part of the agenda is how DoD intends to revamp the program’s annual budget, as well as details about Washington’s adjusted yearly buy rate.

The high-level “CEOs meetings” are held annually, but this one will feature the Obama administration’s effort to restructure the effort after an independent Pentagon cost-estimating group predicted additional cost growth and schedule slips.

For the first time, Hale said, the 2011 defense spending request is based on “independent” price tag projections, which were conducted by DoD’s Cost Assessment and Program Evaluation (CAPE).

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