The Office of Management and Budget issued a much-awaited veto threat on Thursday over the secondary engine for the F-35 Joint Strike Fighter.

The House has started debate on the 2011 defense authorization bill, which currently contains $485 million for the backup engine made by General Electric and Rolls Royce.

But congressional opponents of the second engine have put forward an amendment to strike the funding. OMB has said if the final bill contains the funding for the engine "the president's senior advisors would recommend a veto." Defense Secretary Robert Gates has said on multiple occasions that he would recommend a veto.

The Obama administration also strongly objects to provisions of the bill which could limit the procurement of the 42 aircraft requested by the Pentagon. "The onerous restrictions impose unacceptable schedule and budget risks on the JSF program," OMB said in the statement of administration policy. "If the final bill presented to the President contains provisions that would seriously disrupt the F-35 program, the President’s senior advisors would recommend a veto."