Tokyo — Prime Minister Yasuhiro Naka-sone's new Cabinet took office Thursday amid a growing perception at home and abroad that Japan is an active member of the Western alliance.
As Japan's looming $30 billion trade surplus with the United States foreshadows new frictions across the Pacific, the sense that Tokyo is ''a member of the West,'' to borrow a Foreign Ministry phrase, is an intangible but important asset. It may prove to be Mr. Nakasone's most lasting political legacy.
Nakasone has just won a second two-year term as president of the ruling Liberal Democratic Party, which enables him to stay on as the head of the government. He is the first premier since 1972 to remain in office for longer than two years.
The new Cabinet shows Nakasone's desire for continuity in foreign policy even as he juggles posts to maintain factional balances that are so important in domestic politics. Shintaro Abe stays on as foreign minister and Noboru Takeshita as finance minister. Both are potential prime ministers, but equally, both also play key roles in international affairs - Mr. Abe as day-to-day executor of foreign policy and Mr. Takeshita as point man for the freeing of Japan's financial markets and the internationalization of the yen.
A new appointment, Koichi Kato as defense minister, brings in an articulate, forthright younger politician who began his career in the Foreign Ministry and is fluent in both English and Chinese.
Nakasone has also appointed the first woman minister since the early 1960s - Shigeru Ishimoto - a former nurse who has been active in welfare and the health field for many years. Mrs. Ishimoto is minister for the environment.
In domestic terms, Nakasone's reelection as party president was not achieved without fierce factional disputes that have left him weaker politically. But in foreign policy, what Secretary of State George Shultz refers to as an ''international partnership'' between Washington and Tokyo is likely to remain unchanged.
What he means, US officials say, is that the two Pacific powers are not merely regional allies but that their interests interact on a global level and that the actions each takes frequently reinforce or complement those of the other.
What has been important in Japan's conduct of foreign relations under Nakasone's administration, American officials say, is that Japan is no longer merely a security protege of the US but is beginning to play an increasingly assertive political role in world affairs.
''The days of 'economic giant, political pygmy' are over,'' Undersecretary of State Allen Wallis told a Senate committee Oct. 3.
A US diplomat who has held senior positions both in Europe and in Asia says that these days, Japan is a more overall partner for the US than is Britain, in that Japan interacts with the US in more parts of the world than does Britain. Such a statement would have been unimaginable three or four years ago.
Today Japan is the largest source of economic aid for China, South Korea, and the six countries belonging to the Association of Southeast Asian Nations. It gives economic aid to Egypt, Pakistan, and Turkey - not so much because of their economic importance to Japan, but because they stand on the front line of global strategy vis-a-vis the Soviet Union and are important to the West as a whole.
Abe has been actively trying to mediate the Iraq-Iran conflict. Japan, alone among the Western powers, has good relations with both countries.
These actions have been taken in close consultation with the US. Abe has met Mr. Shultz 14 times in the last two years. Such frequent personal contact is important, Abe told an interviewer not long ago. After all, he said, it is human beings that conduct relations between nations.