Vienna — Despite the exchange of attacks between Italian and Soviet Communist parties over martial law in Poland, restraint by both makes a complete break unlikely.
The Soviet Union, confident that its policies toward Poland will succeed, has no reason to push a full break with Western Europe's most powerful communist party.
The Italian Communist Party, which hopes to participate in a future Italian government, can increase its popularity by demonstrating independence from Moscow over Poland. But there is no reason to force a complete split.
Two years ago, the Russians backed away from an open quarrel with the Western parties over the Soviet invasion of Afghanistan. Moscow hoped to avoid a rift in the international movement comparable to that caused by Soviet intervention in Czechoslovakia in 1968.
They were especially eager to avoid an all-out clash with the Italian party, which has been the biggest and most effective communist party in Western Europe ever since World War II.
A major factor in restraint then was Moscow's confidence that it had weathered the worst of Western reactions - both capitalist and communist - to the invasion of Afghanistan. The Soviets had concluded that they, therefore, need not worry that much, a view that subsequent events seemed to confirm.
Today similar considerations apply. The Russians take the position that Western sanctions will not hurt them, that they are not directly ''involved'' in Poland, that martial law was a Polish decision and, finally, that the Polish government has the situation in hand.
The Italian Communist Party is also seeking to avoid a break. After issuing its stern indictment of Soviet influence behind Polish events, it disavowed any wish to carry the dispute beyond a firm demand for respect of interparty relations based on ''parity and autonomy'' - that is, as set out in the East Berlin agreement of 1976.
The Italian party's critical view of the Soviet party and its ideology dates back to Soviet intervention in Czechoslovakia. The Italian position was the mainspring of the ''cold war'' duel that went on between the Kremlin leadership and Western parties allied with the Yugoslavs for five years. The cracks were papered over by the conference of all European communist parties in East Berlin in 1976.
It was above all the Italian party and the Yugoslavs - led then by Tito, the ''heretic'' of 1948 - who finally forced Soviet acceptance of a declaration on the equality and independence of all communist parties and their responsibility for ''socialism'' in their own countries, which these and other parties now accuse the Russians of violating.
For the Soviets, the Italian Communists' most serious offense is the way they have combined condemnation of martial law and its consequences for liberty in Poland with an even more wounding denial of Soviet ''socialism'' as a valid driving force in Eastern Europe, or, for that matter, for ''socialism'' in the contemporary world at large. In short, the implication of the Italians' position is that the Russian model has ''run out of steam.''