Japan to use US F-16 as its future fighter plane. But Tokyo will use only basic design, wholly modified at home

After two years of debate, Japan's Defense Agency has chosen an American airplane as the basis for its new jet fighter. The General Dynamics Corporation's F-16, officials said, will be Japan's support fighter, codenamed FSX.

The decision, though not yet officially announced but confirmed by knowledgeable sources, is widely viewed as a major concession by Japan to the need to maintain close security ties with the United States.

Japanese defense officials had earlier favored domestic development of the plane, a course strongly urged by its aerospace industry.

United States congressional and defense officials had called instead for Japan to purchase an American jet.

According to well-informed sources, however, the Japanese intend to use only the basic design of the F-16 fighter's body.

The Japanese, the sources say, told General Dynamics and US defense officials last week that they require the use of Japanese-designed equipment for all of the plane's sophisticated electronic systems like radar and onboard computers.

The plane will have to be extensively modified, they say, to meet Japan's requirements. In addition, they are asking that the production of the plane take place entirely in Japan.

The Japanese plane, says one informed American source, ``is as close to domestic development as you can get with a US airframe.''

The FSX issue has been linked by congressional leaders to Japan's huge trade surplus with the United States.

Senator John Danforth (R) of Missouri had earlier pressed Japan to buy an American plane, arguing it would be a more cost-effective decision than domestic development.

The senator, a leader on trade issues, accused Japan of barring its market to a superior United States-made product. Mr. Danforth praised the initial decision, announced earlier this month, to drop the domestic development option and choose either the F-16 or McDonnell Douglas Corporation's F-15.

However, the American source says, the Japanese plan will produce few, if any, jobs for American workers.

Japan currently builds the F-15 fighter under license from McDonnell Douglas. According to company officials, about 40 percent of the contents of the plane comes from the US.

In the case of the FSX fighter, however, Japanese officials want to reduce that to zero.

The decision in favor of the F-16 Fighting Falcon, over the rival F-15 Eagle, was mainly based on cost, a Japanese official explained.

The unit price of the F-15, a sophisticated interceptor, is almost twice that of the lightweight F-16 fighter.

Japan plans to build at least 100 FSX fighters by the mid-1990s. The F-16 cost per plane, Japanese officials say, is estimated at 5.5 billion yen (about $38 million).

The aircraft is to be used mainly for defense against ships and for ground attack, with a secondary role as an air combat interceptor. It will replace an existing fighter, Japan's only domestic-made supersonic plane.