Soviets wonder how to respond to US moves

China . . . Cambodia . . . Pakistan . . . Afghanistan. . . . The Reagan administration, as viewed by Moscow, has declared the diplomatic equivalent of war on the Soviet Unuon.

The result could be internal pressure on the Soviet leadership to reply with more than the now-familiar howls of its official news media.

A possible corollary: a long-term crisis in East-West relations, even should the Soviets resist the urge to intervene in Poland. So, at least, suggest various senior Soviet officials privately.

Whether this scenario proves correct is probably the most important question raised by new US assertiveness toward Moscow. Soviet rhetoric makes nice headlines. But it is ultimately a mere footnote to world history. What matters is Soviet policy, Soviet actions.

In recent days, the Reagan administration has made two moves that cause particular concern in the Soviet Union, no doubt because they go beyond the mere hard-line words that Moscow so avidly answers in kind.

First, agreement was announced on a large package of US military and economic aid to Pakistan, one frontier away from the Soviets' estimated 85,000 troops in Afghanistan.

Then Washington announced it was lifting the formal ban on considering arms sales to China, the Soviet Union's neighbor and bitter (if militarily much weaker) rival.

The tough US words also continued. US Secretary of State Alexander M. Haig Jr., attending a conference of noncommunist Asian states, was quoted as saying the Americans would not stand idly by while Soviet-allied Vietnam left 200,000 occupation troops in Cambodia.

The Soviet response to US moves on the Pakistani and Chinese fronts was prompt, ominous-sounding ("dangerous" was a word the Soviets used repeatedly), but still in the realsm of talk, not action.

The superpower exchange could yet be dwarfed by a Soviet move in Poland. Although the Soviets have still given no public sign of their intentions, officials and the state media have been steadily increasing pressure on the Poles and making clear the Kremlin's alarm at the approach of a planned July 14 congress of Poland's ruling communists.

And Poland is an issue off by itself in many ways. Diplomants generally reject suggestions that the US hard line toward Moscow might prompt the soviets to conclude that detente -- and its economic benefits -- is lost anyway, and thus march gleefully into Poland.

There seem to be many other factors figuring in the Soviets' hesitancy to intervene. These include the possibility that such a move could cause bloodshed but not fundamentally resolve the Kremlin's Poland problem."

Besides, on the superpower front the Sovi ets still seem sure to get arms talks with the Reagan administration if there is no Polish intervention, and not to get them for a long time if there is.

But leaving aside the Polish crisis, one senior Soviet official suggested that Reagan administration foreign policy was serving to strengthen internal opponents of President Brezhnev's public bid for renewed superpower dialogue. Other officials imply privately that Foreign Minister Andrei Gromyko, who has more diplomatic experience than the rest of the 14-man Poliburo combined, could emerge as one such opponent.

This cannot be independently confirmed. Westerners who met recently with Mr. Gromyko said it was their impression with Mr. Gromyko said it was their impression he had not "given up hope" on eventually improving relations with the Reagan administration.

US diplomats, speaking privately to European colleagues, argue that Soviet talk of a hawk-vs.-dove equation is very possibly designed to encourage pressure for US moderation. They say it is high time Washington got tough with a superpower rebels worldwide and troops of Afghanistan.

Besides, Mr. Brezhnv has shown an ability to ignore selectively aspects of US policy publicly criticized here to get talks he wants. One example: his willingness to welcome then-President Richard M. Nixon to Moscow in 1972 against a background of escalated fighting in Vietnam.

But by that time it was clear the US was paying for, much more than profiting from, involvement in Vietnam. Now it is the Soviets who are bogged down in Afghanistan. They also face q quitessential Hobson's choice over Poland. They take their historic rivalry with China seriously, despite their clear military superiority on that front. All this is at a time when, Soviet official argue, the Americans are pursujing a policy of "anti-Sovietism" worldwide.

At least some veteran Western experts canvassed here see reason to put credence in the Soviets' privately voiced concern, and implicit warnings, over Reagan administration policy. Mr. Brezhnev has no democratic electorate to answer to. The inertia of Soviet politics, and the age of his fellow Politrburo members, would seem to militate against any open challenge to his power.

But political power here hinges on at least the image of strength. Or so many Russians feel. And What Russians believe presumably helps determine how Russians act.

Nor does the absence of democracy necessarily means that men like Mr. Brezhnev can -- or want to -- be unmindful of concerns among those who hover around them near the summit of Soviet power.

Mr. Reagan's open challenge to what he sees as worldwide Soviet aggression comes at a time when just about everything Mr. Brezhnev has touched has turned out to look very little like gold: the Polish crisis, the domestic economy, and now, increasingly, "detente."

Some analysts here suggest that -- regardless of whether the last problem is Mr. Brezhnev's fault, as US officials maintain -- he could conceivably feel constrained to somehow demonstrate that the Soviet Union is not willing openly to be pushed around.

This need not imply a head-on superpower clash, something neither superpower presumably seeks. But it could, these analysts aregue, mean some form of reassertion of the very Soviet "misbehavior" Mr. Reagan is pledged to counter.