A Soviet invasion of Poland would have extremely serious repercussions inside the Soviet empire that it would be designed to protect, according to U.S. specialists.

While attention generally has been focused on the impact on East-West relations, specialists on the Soviet Union and Eastern Europe have been watching the Polish drama with fascination and foreboding in anticipation of major new economic and political strains in the East bloc.

The specialists do no agree on the likelihood of a Soviet invasion, some of them believing that such action may be imminent and others believing that the Russians are still bent on using military pressure and intimidation, rather than force, to work their will in Poland.

The experts agreed, however, that if an invasion comes, the scale and perhaps even the nature of its repercussions would hinge to a large degree on the extent of the resistance.

If the Russians could quickly subdue Polish opposition on something like the pattern of the interventions in Hungary (1956) and Czechoslovakia (1968), the consequences in the Soviet bloc would likely be manageable though serious, the experts said.

But if the Polish army and people resisted over a period of months -- leading to bloody battles, guerrilla war, sabotage and passive resistance -- then "all bets are off" regarding the future stability of the Soviet bloc, according to several specialists. The uncertainty would be heightened if other Eastern European armies participated with the Soviets in Poland, the experts said.

In case of protracted trouble, a Polish intervention could be an international turning point of the utmost importance, bringing about unforeseeable changes in power relations within the communist world as well as between East and West. For a time, at least, such instability would make the international environment even more dangerous and its management more complex.

While the turbulence in Poland has historical and political roots, it also can be seen as an Eastern European outcropping of the economic troubles that afflict most of the world in this first year of the 1980s. Poland's economy simply has not produced results that its people are willing to accept, and the consequence has been strikes leading to establishment of semi-independent labor unions that threaten the authority of the Communist Party.

A Soviet military intervention to quash the new union movement would not solve Poland's underlying economic problems. On the contrary, specialists said such military action probably would make the problems much worse because of the reaction of the Polish people.

A senior official of one of the New York banks that has participated in large-scale loans to Poland said that, in case of Soviet military intervention, Poland would "become a welfare state which would have to be maintained indefinitely by the U.S.S.R." The official, who asked not be quoted by name, estimated that it would cost the Russians $3 billion to $5 billion a year simply to maintain a "depressed standard of living" in a post-invasion Poland.

This sum, the official noted, is about twice the estimated Soviet yearly outlay to support Cuba, and roughly three times the reported Soviet outlay to Vietnam. Such an increase in external obligations would be a serious matter for a Soviet Union encountering major economic troubles of its own, he added.

In order to preserve a place for Poland in the world economy and to protect the credit of the Soviet Union and other Eastern European states, the Russians would be likely to make it clear they would stand behind the eventual repayment of Poland's outstanding debt to the West of about $23 billion, the financier said.

Beyond the large direct economic drain, an invasion of Poland would be likely to exacerbate economic troubles in the Soviet Union and possibly other Eastern European countries because of countermeasures from the West, including a drying up of new credit. This prospect is reported to be of great concern to several Eastern European regimes, particularly those in Hungary, Czechoslovakia and East Germany.

Growing economic stress in Eastern Europe would likely contribute to political stress resulting from a Soviet invasion.

Seweryn Bialer, director of the Research Institute on International Change at Columbia University, said that a Soviet intervention in Poland that is "successful, not prolonged and does not involve guerrilla war" probably could be sustained without major political repercussions in the Soviet Union and other Eastern European countries. He noted that the ruling communist elites in all these countries consider the Polish unions a threat to the system, and that anti-Polish sentiments in several countries would work to lessen sympathy with Polish workers.

Marshall Shulman of Columbia University, until recently the senior State Department specialist on Soviet affairs, said the political repercussions could become "speculative," even within the Soviet Union, if a Soviet invasion turned out to be bloody and prolonged. Shulman said that against this must be measured the cost to the ruling Soviet elite if the situation in Poland cannot be brought under control without an invasion. "No Soviet leadership could survive the loss of part of the Eastern European empire, in my opinion," Shulman said.

Vladimir Petrov of George Washington University said that "a military demonstration" in Poland would be broadly supported, but that heavy fighting with serious casualties to the invaders would be another story. "Dying in Poland is not a sacred cause . . . Poland is vitally important to the Soviet elite, but not to the ordinary people," he added.