WASHINGTON (Reuters) - A House of Representatives subcommittee defied White House and Pentagon leaders on Tuesday by including $485 million in the proposed U.S. military budget for an alternate engine for the largest weapons program ever - the F-35 fighter jet.

With a veto threat hanging over the massive fiscal 2011 spending package, the defense appropriations subcommittee voted 11-5 to proceed with the engine being built by General Electric Co and Britain's Rolls Royce.

The White House and Defense Secretary Robert Gates view the second engine for the Joint Strike Fighter as wasteful in an era of big-budget deficits and want it cut from the budget.

This is the fourth time in four years military planners have tried to end the alternate program, and the fight is far from over with the Senate still to address the issue. A final defense budget, proposed in the House at $671 billion, is not expected for months.

The defense panel's chairman, Representative Norm Dicks of Washington state, also objected to expanding engine development. Both engines, if built, are worth up to $100 billion in business, according to industry estimates.

Pratt & Whitney, a unit of United Technologies Corp, builds the main engine for the next generation jet fighter being developed by Lockheed Martin Corp in partnership with eight other countries.

Alternate engine supporters in Congress believe the added competition, which the administration has demanded in other weapons programs, will reduce costs and improve F-35 performance overall.

Preserving jobs in key states is also a plus for lawmakers facing voters this November.

The Pentagon also wants lawmakers to stop funding further orders of the C-17 cargo plane made by Boeing Co.

(Reporting by John Crawley; Editing by Tim Dobbyn)