Washington: The new Chairman of the Joint Chiefs of Staff put Capitol Hill on notice today, telling lawmakers that DoD may not be able to afford all three versions of the F-35 Joint Strike Fighter.

In his first appearance before House Armed Services Committee as chairman, Gen. Martin Dempsey said that buying the Air Force, Navy and Marine Corps versions of the fighter up and running may just be too expensive.

Dempsey’s comments came after the four-star general was pressed by panel members on whether the Pentagon is committed to the Marine’s vertical-lift version of the plane.

In response, Dempsey said he was fully dedicated to buying a “fifth-generation fighter,” but he did not mention the JSF by name. However, he said buying all three variants would greatly increase pressure on an already stressed budget.

Development delays and cost overruns forced former Defense Secretary Robert Gates to put the Marine Corps plane — known as the F-35B — on a two-year probation, after which DoD could terminate the program.

Marine Commandant Gen. James Amos, an aviator himself, has said repeatedly the plane will be ready to go well before that two-year period is up. The jet recently completed initial carrier flight tests earlier this month.

The Marines are already feeling the strain of not having the JSF in its inventory. The service is already pushing the envelope on flight hours for its fleet of AV-8B Harriers — which the F-35 is designed to replace — and F-18 Hornets.

The only reason the Marines decided not to buy the more advanced F/A-18 Super Hornet to replace the older versions of the fighter is they assumed the F-35 would be ready to go by 2012, Lt. Gen. Terry Robling, deputy assistant commandant for Marine Corps aviation, said last month.

Now those planes aren’t expected to come into the fleet until 2014, and the Marines are considering pulling JSF funds to extend the lives of their old Hornets.