East German chink in Soviet armor.

The summer lovers' spat between East Berlin and Moscow - if mishandled by the Kremlin - could turn into the greatest postwar challenge to Soviet hegemony in Eastern Europe.

The risk is great - first, because this time it's the Germans who are pressing for more elbowroom; second, because they could be joined by other East European states in an unprecedented joint push; and third, because the Soviet leadership is old and tired.

On the face of it the Soviet-East German quarrel is trivial. Erich Honecker, party and state chief of a nation long ostracized in the West, wants to make his first official visit to West Germany next month. To do so, he is willing to improve the bilateral atmosphere by modest liberalization, especially in easing some travel restrictions for East and West Germans visiting each other.

The Kremlin, which initially approved the Honecker trip, doesn't mind the substance of the deal all that much. But it abhors Mr. Honecker's timing and style. It dislikes having East European clients wink at Moscow's current scowl over NATO missile deployments and the American election. And it intensely dislikes the public precedent of the West's extracting humanitarian concessions from the Soviet bloc by monetary bribe - in this case a $330 million credit from Bonn to East Berlin.

The East Germans, in turn, don't like being pushed around by the Russians or anybody else.

With this clash of psychology rather than hard interests, Moscow and East Berlin can presumably kiss and make up if the Soviets show a little more tact.

But tact is hardly a Soviet forte, especially where Germans are concerned. The Russians, who for centuries have combined admiration and envy of the technologically adept Germans, had their national emotions intensified by German invasions in World Wars I and II. Their nightmare (however nonsensical it might seem from any objective comparison of military power) is that one day a reunited Germany might turn against them.

Partly because of this angst, East Germany is the only East European country in which Soviet divisions (19) outnumber host-country divisions (6). Until the recent Soviet leadership of Yuri Andropov, the Soviets kept an ambassador in East Berlin who behaved like a proconsul. And in a further anti-German stance prior to detente, and again since last spring, the Soviets have relied heavily on East European fears of the (West) Germans to justify Soviet hegemony in East Europe.

Today East Germany is clearly the Soviet Union's most important ally, since it is on the front line with NATO. And insofar as East Germany has established an identity of its own in the decades since World War II, it has been far less self-confident than West Germany. This identity has consisted of being the most loyal and orthodox Soviet ally (after Bulgaria).

East Berlin has no intention of abandoning this role. Indeed, a precondition for the present warm East-West German relations was Bonn's full acceptance of East Berlin's active adherence to the Soviet bloc. Yet East Germany feels it has earned the right - especially by its full support for Moscow in the Soviet-Polish feud over Solidarity - to expand a bit its own discretionary space in foreign policy.

In a notable escalation of Soviet-East German polemics, a Central Committee-approved editorial that appeared Aug. 1 in the East German Party newspaper Neues Deutschland made this abundantly clear. It reiterated East Berlin's foreign-policy goal of damage limitation in East-West relations - on the basis of both East and West German ''independence'' in domestic and foreign affairs.

The high-level Pravda riposte yesterday made it equally clear that the Kremlin expects East Berlin to leave even modest foreign-policy initiatives to Moscow. It specifically denounced the concept of damage limitation (while disingenuously attributing this concept to West German Chancellor Helmut Kohl). And it again accused Bonn of trying to undermine East German sovereignty and socialism.

The latest exchange suggests that the spat is intensifying. Here again, psychological and political factors add a self-perpetuating element.

The East German leaders are acutely aware that in the past they have been the laughingstock of Eastern Europe for their subservience to Moscow. They think they have now outgrown such a relationship, and they want the Soviets to acknowledge this. They know that theirs is the greatest success story of the Soviet bloc, economically and socially. They have become sufficiently self-confident in recent years to take pride in German (and not just proletarian) history. They want to be treated with dignity.

This dignity the West Germans now accord them. The Soviets do not.

For the East Germans, then, the standoff of August 1984 is altogether different from the impasse of the early '70s between a Leonid Brezhnev who wanted detente and a Walter Ulbricht who desperately wanted to avert detente. Not only are the roles reversed. This time around Honecker has so packed the Politburo with his own men that Moscow cannot now dump him as easily as it once dumped the bothersome Herr Ulbricht.

In the current argument an East German leadership that feels itself maturing faces a Soviet leadership that feels itself declining. The elderly interregnum in Moscow looks at Soviet economic and technological stagnation, at tensions between various Soviet nationalities, and at possible Soviet overextension in Afghanistan and in any simultaneously restive Eastern Europe. It is alarmed by change, and it therefore tries to force East Berlin back into the familiar status quo. Yet it is this Soviet immobilism that tempts East Germany and other East European countries to test how much new leeway they might have gained in a quiescent Soviet phase.

Ironically the more Moscow now tries to compel East German conformity, the more it stimulates the very thing it fears: a considered East European reisistance to its pressure. In the past only one client at a time has tried to slacken the ties to Moscow (except for Hungary and Poland after Soviet de-Stalinization in 1956), and the Soviet Union has generally been able to rally other concerned East European leaders to prevent developments from going too far.

Now, however, all the Soviet-bloc governments in East Europe except for Prague are either cheering the East Germans on or are neutral in the dispute. Hungary, which has been preaching the special role of medium-size European states in preserving a modicum of detente, ostentatiously praised the East Germans in a newspaper article July 28, the day after Pravda first denounced East Germany's relations with West Germany.

Romania, like East Germany, has been letting it be known that it regrets the stationing of new Soviet missiles in East Europe (and the compulsory East European financing of them) following the first NATO deployments at the end of 1983. More puckishly, Romania is also participating in the Los Angeles Olympics this week despite the Soviet-bloc boycott.

Surprisingly, even Bulgaria has published cautious comments this week indicating sympathy with East Germany - and party and state chief Todor Zhivkov seems to be going ahead with plans to visit Bonn ahead of Honecker.

Poland, ever sensitive to potential West German claims to former German territory in Poland, has been willing to join the Soviet Union in criticizing West German ''revanchism'' in recent months. It has not, however, joined in Moscow's and Prague's condemnation of Hungarian and East German hopes for modest European detente in the midst of superpower tensions. And few people doubt that if East Germany manages to win more elbowroom for itself then the volatile Polish man in the street will again begin demonstrating for a restoration of the banned trade union, Solidarity.

The upshot is that although the highly orthodox East Germans are now moving only millimeters (in comparison with the Yugoslavs in 1948, the Hungarians in 1956, the Czechs in 1968, or the Poles in 1980), they could be initiating a far broader movement than did any of their fellow East Europeans.

This is precisely what the Soviets fear. And it's no comfort to them to realize that their fateful disputes with the Yugoslavs and the Chinese back in the 1940s and '50s were conducted with client communist regimes that were then the most orthodox in the Soviet bloc.