PERSPECTIVE ON SUMMITRY : Bipolar Machine Running on Empty : Once, superpower meetings made sense. These days, the world is multipolar and two-party summits mean less.

Will this be the last bilateral summit meeting between the leaders of the United States and the Soviet Union? Perhaps not. Institutions always take time to catch up with reality, and winding up an old institution almost always takes longer than building up a new one.

It is easy to imagine, especially if you are too young to have a clear memory of the early postwar era, that all postwar history has been punctuated by such summits. We have been told often enough, after all, that the postwar world is or was a “bipolar” one. But actually the first bilateral U.S.-Soviet summit was held in 1961, between John Kennedy and Nikita Khrushchev. Previous East-West summits--in 1955 and 1960--had been four-power affairs. Britain and France were included not by virtue of their actual importance at the time, but because their loss of importance since the period of real four-power diplomacy (1945-47) could not be publicly admitted without awkwardness.

Bilateral summits eventually became more or less regular occurrences just at the time--the 1960s--when the world was ceasing to be bipolar, with the Sino-Soviet split on the Eastern side and the emergence of Europe and Japan as economic powers (not to mention Charles de Gaulle’s demonstrations of political independence) on the Western one. By now, in 1990, they are clearly an anachronism. The only thing that the United States and the Soviet Union can seriously hope to settle between themselves is a strategic arms reduction treaty, because it is only the sheer size of their strategic nuclear stockpiles that still puts them clearly in a class apart from other states. But the rest of the world now feels much less concerned by this aspect of arms control than it did in the past. A direct exchange of nuclear strikes between the two could still be catastrophic for the rest of the planet, but it no longer seems very likely--and it would still be possible even with much lower numbers of weapons on each side than are envisaged in the treaty now being discussed.

For other purposes an exchange of views between the leaders of these two powers may be useful or even necessary, but no more so than the meetings that they each have separately with, for instance, French President Francois Mitterrand. Indeed, discussions are likely to focus, on German unity and the future security structure of Europe, it could be argued that they should be less interested in one another’s views than in those of West German Chancellor Helmut Kohl.

The special build-up given to a U.S.-Soviet summit is a kind of courtesy, just as it was a courtesy to go on treating Britain and France as notionally equal “great powers” in the 1950s. To a certain extent it reflects American self-importance. To a greater extent it is a courtesy to the Soviet Union, and to Gorbachev in particular.

Alas, poor Gorby. An American columnist has compared him to Jimmy Carter. Yet who could deny that America in 1980 was a model of order, prosperity and successful government compared to the Soviet Union today? The question is not merely whether it is a power capable of negotiating on equal terms with the United States, but whether it is going to survive. Seldom can any national parliament have heard a confession of failure quite as abject as that of the Soviet prime minister last Friday: “We have no more money. We have no more gold to buy grain.” Violence in Armenia, the secession of the Baltic republics--these seem like little local difficulties now that Russia itself is threatened with mass starvation, perhaps even civil war, while the government of the Ukraine declares its “firm opposition” to Gorbachev’sreforms.

Up to now Gorbachev has used his popularity abroad, his good relations with foreign leaders (especially those of the United States), and the general aura of success and dynamism surrounding his foreign policy as a means of bolstering his prestige and tiding him through difficulties at home. Like other leaders in other countries before him, he has found that this tactic produces sharply diminishing returns. Worse, the point has now been reached where the main transference is in the opposite direction: It is domestic events that influence international reactions more than the other way round.

In fact it was the changes within the Soviet Union, as much as if not more than those in foreign policy, which brought Gorbachev his great popularity abroad in the first place. The sudden blossoming of pluralism and freedom of expression in what had been the monolithic “evil empire” made it possible to take seriously his talk of “universal human values” and to believe that changes in foreign policy, with the weight of Soviet public opinion behind them, would not be easily reversed. But now even the Soviet leader’s most sincere and enthusiastic well-wishers in the West are obliged to take notice of his growing unpopularity at home and his inability to control events. It seems almost quaint to remember that a year ago Western diplomats were seriously worried that the cautious, lackluster President Bush might prove no match for the charismatic Soviet leader with his bold and innovative vision.

In reality, Gorbachev’s position is now as weak abroad as it is at home. At home he may well be tempted to revert to dictatorial methods and could perhaps expect some support if he did so, given the disastrous material results of his half-hearted economic liberalism. But “administrative command” will not bring food into the shops and it seems very doubtful whether the administrative-repressive machine would any longer respond to Gorbachev’s touch. If it did so, it might well be only for a short period before he was either replaced by a more consistent and resolute authoritarian or swept away by a new explosion of popular anger.

Abroad, he cannot now, after allowing a free election in East Germany to produce a government committed to unification, use the Soviet forces there to prevent that program from being carried out. Nor can he prevent the united German state from deciding for itself whether it wishes to remain in NATO, and if so on what terms. Nor can he very long keep Soviet forces in Germany if the clear wish of the German people is that they depart. Nor indeed can he force other Central European countries, which now have representative governments looking to the West for economic aid and political inspiration, to take his side in a sudden renewal of the Cold War.

That being so, he must know that to break off “the whole process of negotiations in Europe,” as he threatened in his press conference with Mitterrand on Friday, would damage the Soviet Union much more than it could the West. Its most likely outcome would be the one he most wants to avoid--the exclusion of the Soviet Union from Europe, leaving it to flounder, unaided, in the grim aftermath of communism.

Gorbachev hopes to avoid that by modifying the structure and attitudes of NATO and by persuading the West to join him in building new pan-European institutions. For that he needs the support of Western, especially German, public opinion, and he may yet be able to get it. But uttering empty threats is not the way.