The Reagan administration's economic sanctions against Poland and the Soviet Union should hasten negotiations between the Polish government and the trade union Solidarity, a leading Polish dissident said last night.

But Miroslav Chojecki, an associate of arrested Solidarity leader Lech Walesa, added that he could foresee anoptimistic end to the present crisis in Poland, only if the Soviet Union decides that "Poland is necessary to them as a well-functioning social and economic system."

If the Soviets decide that both Solidarity and the government are necessary for a stable Poland, "under the economic pressure of Western nations, we could return to the situation of before December 12," when the government cracked down on the Solidarity, Chojecki said to a sympathetic crowd of about 200 people at Boylston Hall.

Chojecki added that there is only a small chance that such a relaxation of control will occur.

Other more likely scenarios include either the continuation of martial law until resistance is crushed or a decision by the Soviet Union to resolve the crisis itself with a Hungary-like invasion, he said.

Chojecki discounted reports that resistance to martial law is dying down, saying that nearly 80 per cent of workplaces are shut down, that large numbers of journalists have refused to take loyalty oaths to the government, and that there are still police patrols in the streets suppressing dissent.

He added that even in spite of martial law, "there are still uncensored publications going around in Poland." Chojecki, before coming to the United States in October of 1981, founded the independent publishing house "Nowa" and also helped establish Solidarity's printing offices.

Such publishing houses were instrumental in the organizing of Solidarity, he said, adding "the passing of the uncensored information among the workers proved most useful in organizing the strikes" that occurred before the crackdown last December.