Many US soldiers probably watch their favorite shows on Sony TV sets and drive Japanese-made cars. Soon they may also be firing off Japanese-made missiles or driving Japanese tanks for the first time.
That is the possible implication of a precedent-setting agreement soon to be reached by United States and Japanese negotiators here.
Two years ago the Japanese government, in a break from its longstanding postwar policy, agreed to exempt the US from its ban on exporting military technology to any country.
Now the Japanese are readying the first delivery of military hardware, the prototype of an advanced shoulder-fired surface-to-air missile (SAM) being developed by the Japanese Defense Agency.
Under the agreement, the missile prototype will be brought to the US to be tested at Defense Department facilities. Actual production -- if the weapon proves to be of interest -- would be negotiated later under a separate agreement.
US defense officials are hopeful that this test-case accord will open the door to what could be a potential treasure-trove of Japanese high technology.
Japanese electronics technology, for example, could make a vital contribution to the Reagan administration's Strategic Defense Initiative (SDI) research.
Japanese and US negotiators met here last week to discuss the details of the arms transfer. According to a senior Japanese Foreign Ministry official, the final agreement should be reached ``in a few more weeks.''
Japan and the US are partners in a 1952 ``mutual defense agreement,'' but until now the flow of defense technology has been a one-way street -- from the US to Japan.
That fact has prompted numerous complaints from across the Pacific that Japan has been using its access to US military technology to build up its commercial industries. Licensed production of US fighter jets in Japan, for example, has aided advancement of its civil-aeronautics industry.
The Japanese government is clearly eager to correct the impression that Japan has always had a ``free ride'' in its defense cooperation with the US. The transfer deal will be a symbolic -- though significant -- gesture of Japan's willingness to break the ice and expand defense collaboration with its ally.
The Japanese missile was formally requested by the US as the ice- breaker last spring. US officials cite two reasons for its selection.
First, the SAM has been developed under the auspices of the Defense Agency's own research lab, making this a purely government-to-government transfer. That avoids, for now, more thorny issues raised by Japanese private-sector participation.
Second, the missile uses new technologies of particular interest to the United States.
It employs a unique twofold system for guiding the weapon to its target. The missile's dual ``seeker'' uses both an infrared device, which homes in on a heat source (such as a jet's engine), and a newly-developed video image seeker, which uses a ``charge coupled image sensor'' (similar to a device used in closed-circuit televisions) to track the target.
Existing SAMs use only one kind of homing device -- usually infrared seekers.
US officials are most interested in how the Japanese have used advanced-integrated-circuit and computer technology to unify the two devices into one system.
``We hope it is worthwhile to us,'' one US defense official said.
Progress toward the agreement has been slow in coming since the initial 1983 Japanese announcement.
US officials have been seeking the conclusion of an umbrella agreement, which would include all future transfers and allow for both testing and production.
The Japanese side, under political pressure from opposition parties that oppose any defense-related exports, have insisted on a cautious, case-by-case approach. A compromise formula is being sought.
Japanese defense contractors, which include some of the country's biggest companies, have been reluctant to be the first to break the no-export barrier. Japanese defense-industry sources say they fear the potential public relations fallout here, where such issues are still highly sensitive.
And Japanese companies, mirroring their United States counterparts, are also concerned that they will lose control of valuable commercial technologies by giving the US access to some defense-related equipment.
Japanese firms prefer to sell so-called ``dual-use'' technologies -- things like computers, computer chips, or fiber-optics which have both commercial and military uses.
For example, Japanese participation in Reagan's SDI program will, if it occurs, likely take place under this label. Dual-use technology does not fall under the 1983 policy and is not now restricted for export from Japan.
A US Defense Department technology team that visited Japan last year issued a report earlier this year outlining a number of areas of Japanese technological expertise that could be of use to US defense efforts.
Among the items on a potential US shopping list are: fiber-optics; night-vision devices; heat-resistant ceramics; gallium-arsenide, the computer-chip material of the future; lasers; and fifth-generation computers, still in the research phase. The last three technologies are considered crucial for the SDI program.