HOW DO YOU properly congratulate your principal military and ideological adversary on its 60th birthday? By acknowledging the economic and social gains the Soviet Union has made since the Bolsheviks picked up the power lying in the streets of St. Peterburg in 1917? By nothing that the Kremlin is, by virtue of its military reach, a global power on a plane with the United States? These are, in fact, the things that the dozen or so people who count in Moscow solicit respect for, and no clear-eyed observer of the Soviet scene will deny them their due.

But something must be added. The Soviet Union still surrounds itself with an iron curtain - literally, machine-gun towers and barbed wire - to keep its citizens from fleeing. It still maintains educational and judicial systems designed to force the people into pattern dictated by a few unelected leaders. It is still frightened of its own subjects, whether they be dissidents wishing to take literally the lofty rights inscribed in official pronouncements or nationality groups finding Kremlin power a straitjacket for their ethnic aspirations. Sixty years of Soviet communism may even have shrivelled the sense of voluntary and conscientious commitment to public purposes that ideally defines a citizen's attitude to the state. If there is a single idea that the Soviet Union now stands for, it is not communism, whatever that may mean, or egalitarianism or non- exploitation or development but centralized bureaucratized power.

Whether the Kremlin's domestic policy and values ought to affect the American attitude is, of course, a hotly debated question. Mr. Carter's answer is that the United States should care about "human rights" but this should not crimp efforts to improve relations in other spheres. This is a reasonable way to address the complexity of American interests. Soviet domestic performance does evoke a concern for rights, and Soviet power does compel a concern for political coexistence.

But is evident that nothing would be more likely to get Americans to deal more closely with the Kremlin than a belief that it was treating its own citizens with decency and respect. The alien values and the arbitrariness and the lack of accountability suggested by teh Soviet style of governing cannot fail to stir our anxieties. If, as Mr. Carter suggests, we have lost our "inordinate fear of communism," there remains a substantial "ordinate" fear.

With or without a demonstration of Kremlin mellowing, the political leaders and diplomats of both countries have an inescapable responsiblity to try to make their nations' continuing competition and hostility less dangerous, and to broaden whatever fields of productive cooperation can be found. But without such a mellowing on the Kremlin's part, itis hard to imagine that Americans will hail the next round-numbered Soviet holiday with any more gladness than the 60th.