President Bush will propose major changes in a controversial U.S.-Japan fighter plane project, ones that would protect sensitive U.S. technology, administration and congressional sources said Tuesday.

The sources said that a final decision on the so-called FSX project will likely come on Wednesday or Thursday.They said that the key modification to be sought by Bush in the agreement negotiated late in the Reagan administration concern the "source codes" that enable the jet's computers to fly the plane.

However, it was not clear at this point whether the president would seek a complete rewrite of the original agreement to include these safeguards or would seek Japanese approval of side-agreements, the officials said.

Japan's ambassador to the United States, Nobuo Matsunaga, was called to the State Department on Monday for a meeting with Secretary of State James A. Baker III and other top administration officials to discuss the proposed modifications.

At the session, the new U.S. position "was explained to Matsunaga," said Shingo Yamagami, an official in the Japanese embassy.

He declined to give specifics on the disucssion.

However, he said the Japanese government still "strongly hopes this agreement will be implemented" despite the "many viewpoints" both in Congress and within the administration over it.

B. Jay Cooper, a White House spokesman, said Tuesday that "no final decison" had been reached yet by Bush.

However, Republican congressional sources, who spoke on the condition of anonymity, said that Bush in general was leaning toward tight restrictions on the transfer of U.S. technology favored by Commerce Secretary Robert Mosbacher.

The Washington Post said in its Tuesday editions that Monday's meeting with Matsunaga was a sign Bush had made key decisions over the weekend about placing restrictions on the technology that would be shared for the design of the new fighter plane.

The compromise, the Post quoted sources as saying, is that sensitive data will be shared for the project but with restrictions designed to prevent Japan from applying the technology to other aircraft.