On the surface, the Japanese government is moving calmly and without much hesitation toward a decision to join the United States' ``star wars'' program. But beneath the calm, government officials involved in the final stages of decisionmaking are anxiously hoping to steer clear of potentially serious obstacles. There has been much speculation here that Prime Minister Yasuhiro Nakasone wanted to deliver a positive response to President Reagan on the space-based Strategic Defense Initiative (SDI) before the Tokyo summit early next month. But according to an informed government official here, the SDI decision will probably not be made until after parliamentary elections scheduled for late June.
The decision, the official suggested, is ``too politically sensitive,'' indicating concerns that the opposition parties will seize upon SDI as an election issue.
Japanese private industry, which sent representatives of 21 companies to the US earlier this month to study SDI technology, has its own fears. Industry leaders worry that if they bring their advanced technology to SDI, the US will subsequently classify the work and prevent them from using it commercially.
A US insistence on tight security arrangements for participating Japanese companies could pose serious problems. ``It all depends on the legal framework. If the US government is going to introduce fairly strict rules, the industries will be quite hesitant'' to participate, said a Japanese government official.
The Japanese had the impression from remarks made recently by Defense Secretary Caspar Weinberger that, as a Japanese Foreign Ministry official put it, ``he was content with the existing security protection system that Japan has.'' But the Japanese got a much different opinion in meetings this past week with Richard Perle, assistant secretary of defense for international security.
In an interview, Mr. Perle indicated concerns about the ability of Japanese laws and regulations to protect classified information. ``The Japanese legal structure with respect to espionage of the more classical sort is, as I understand it, inadequate. And the penalties for the illegal export of advanced technology are not sufficient to deter that activity,'' Perle said. Asked if changing that structure would be a precondition for Japanese participation in SDI, Perle replied that he considered it ``an open question.'' During any negotiations on SDI, he said, ``I think we will need to understand better what security arrangements the Japanese can provide for those parts of the program that are sensitive.''
Japanese officials are decidedly unhappy with such views. ``We feel confident to do this within existing laws and regulations,'' said a Foreign Ministry official who met with Perle. ``There has been no evidence of leakage of classifed information to East-bloc countries.''
The official, referring to Mr. Weinberger's remarks on this subject, said, ``there are other views than Mr. Perle's. The Americans are pragmatic people. It's a trade-off situation for the US -- if the US wants Japanese technology very much, then they can be lenient in negotiations.''
An ad hoc group of five Cabinet ministers will meet this week to receive the report of the joint government-private sector mission that visited the US, according to a Foreign Ministry official. The report, most of which is classified, assesses the value of Japanese participation ``from a technological point of view,'' including ``any spinoff effect on Japanese industry.''
The report, the official said, provides a unique ``comparison of who is more [technologically] advanced.''