Congressional critics of the FSX warplane deal told a Senate panel Wednesday that the United States would get the worst of the bargain in sharing with Japan technology used for America's F-16 fighter.

"The evidence before us is that we're really not getting anything in return," Sen. Alan J. Dixon, D-Ill., said in testimony before the Senate Foreign Relations Committee.Advocates of the FSX agreement, which involves co-producing an advance version of the F-16, have said the United States would gain access to Japanese composite wing construction and phased array radar technologies.

But Dixon said a study by the General Accounting Office, an investigative arm of Congress, has found that U.S. companies already have such technologies.

Sen. Alfonse D'Amato, R-N.Y., called the arguments on the technology flowback from Japan "total nonsense and a facade to cover up the shortcomings of this deal."

The FSX deal was strongly defended at the hearing by a panel of senior Bush administration officials, including Commerce Secretary Robert Mosbacher.

"I am confident that this agreement will not harm the economic security interests of the United States," Mosbacher said.

President Bush last month approved a $7 billion agreement under which the United States and Japan would co-produce an advanced version of the F-16 fighter.