For more than a year, General Electric has been notable among U.S. corporations for enjoying generally friendly relations with the White House. The company was broadly supportive of President Obama's stimulus efforts, and its chairman, Jeffrey Immelt, sits on a White House economic advisory board.

But now the White House and GE are clashing publicly over a fighter-jet engine -- built by the company and its British partner, Rolls-Royce -- that has been on the Pentagon's chopping block for years, only to be rescued repeatedly by Congress. The issue is poised to come to a head Tuesday during a House subcommittee markup for the annual defense appropriations bill, which Obama has threatened to veto if it has the $485 million for the engine.

GE -- whose financing arm received billions of dollars in federal bailout funds -- has launched a furious lobbying and media effort in recent months aimed at securing funding for the engine, which would serve as an alternate for Lockheed Martin's F-35 Joint Strike Fighter. Pratt & Whitney, the Pentagon's choice for developing an F-35 engine, has fired back with a lobbying and advertising campaign of its own.

The dispute underscores the latest effort by Obama and his defense secretary, Robert M. Gates, to target costly defense projects in the face of avid support on Capitol Hill. The battle not only threatens the fate of the Pentagon's budget, it could also interfere with the Obama administration's plans to move ahead with a repeal of the military's "don't ask, don't tell" policy on gay men and lesbians, which is included in the legislation.

"The signals have been pretty clear that this is a very serious veto threat," said Thomas A. Schatz, president of Citizens Against Government Waste, which has been sharply critical of the GE project. "It's very unusual to see such a unified front on this kind of project."