For all anybody here can know for certain, as of this writing, Kremlin leaders may already have decided that massive military intervention in Poland is inevitable -- and never mind the impact on East-West relations.

But suppose they haven't? Suppose, further, that their estimate of what is tolerable in terms of the "integrity" of the Polish Communist Party is at least influenced to some degree by what the cost of a bloody Polish repression would be in their economic dealings and other relations with the West in general, but with Western Europe in particular. Their reading -- or misreading -- of Western European sentiment then becomes crucial.

And on that score, say some leading authorities, the Reagan administration may inadvertently be compounding the odds that the Soviets will dangerously miscalculate the prospective European reaction -- and thus heightening the risk of full-scale and brutal intervention.

How? By the very ferocity of the administration's efforts to mobilize the Western alliance against worldwide Communist expansion.

The administration's aim is understandable, if you accept the Haig/Reagan reading of Soviet intent -- in El Salvador, the Persian Gulf, worldwide. The purpose of the great alarums and excursions of the past two months is to unite the West and to rally it against an increasingly menacing Soviet challenge.

Hence the demands for a greater European defense effort and the public denunciation, in scathing terms, of "outright pacifist sentiments" in Europe, by White House National Security Adviser Richard Allen. But the effect, according to European and American authorities alike, is to alienate significant segments of European opinion, weaken support for bigger defense outlays, fan neutralism, complicate political life for important European leaders and contribute to precisely the impression of allied disunity that the administration is supposedly trying to dispel.

A case in point is reported by a participant in a recent conference of American and German officials and opinion-makers. On hand was Richard Pipes, the Harvard professor and Soviet expert, now serving on Allen's national security staff. His blunt message to the Germans: If you want a voice in matters having to do with allied security, you must be ready to shed German blood in the Persian Gulf.

In other words, what Pipes reportedly was demanding is not just a larger German defense effort in Europe to compensate for a larger American presence in the Mideast; he was suggesting something the West Germans have adamantly resisted up to now: the deployment of their forces anywhere outside the NATO area.

"Even though there were a lot of solidly pro-American Germans in the room the effect was electric," according to an American who was there. "The Germans were obviously put off and said as much. That kind of talk can only lead them to distance themselves from American policy, in a way that sooner or later finds public expression."

Ironically, this sort of encounter, by no means isolated, is probably producing more West European dissent from the American line than actually exists -- particularly with respect to the Polish crisis. Most experts agree that if the Soviets actually move in with troops in large numbers, the public reaction in Western Europe would be more than strong enough to support tough economic and diplomatic reprisals.

"This would not be like Czechoslovakia in 1968, when the chill in East-West relations lasted maybe six months," says one expert. He and others cite obvious differences: the likelihood of protracted fighting and loss of life in an East European country with close ties to the West; the fact of a second Soviet repression, only a little more than a year after Afghanistan; the importance of the Catholic Church in Poland; the distraction of Vietnam in 1968; an almost certain refugee problem, including the possibility, as one close observer puts it, of "boat people in the Baltic."

Some authorities foresee an East-West chill that could last for several years. But all that would be after the fact. The critical question, for whatever chastening effect it can have on the Soviets, is what the Soviets see right now.

And the danger is that what they see increasingly in Western Europe is a marked disinclination to follow the American lead. "If we push the Europeans too hard or too publicly -- if we present them with a stark choice when they have their own internal political problems, instead of practicing measured diplomacy -- the Russians may read neutralism and anti-Americanism in the European response," says one Soviet expert.

The result could be to rob the West of whatever deterrent influence it can exert on what one expert describes as the "most important Soviet decision since World War II."