Soviet officials have refused a standing invitation to visit Walter Polovchak and attempt to persuade the teen-ager, who is seeking political asylum, to return with his parents to their native Ukraine, the youth's lawyer said yesterday.

Polovchak, 13, and his sister, Natalie, 18, refused to return to the Soviet Union last summer with their parents. They are free to return at any time, attorney Julian Kulas said.

"We're not standing in their way. They're free to go," Kulas said, reacting to a note to U.S. officials earlier in the day in which Soviet officials demanded the "release" of the two teenagers.

Polovchak, who made international headlines a year ago with his refusal to return to the Soviet Union, has been living with a foster family and will complete the seventh grade within a few days, Kulas said.

The note to the U.S Ebassy said that the parents, Michael and Anna Polovchak, are unable to return to their homeland because their two children are being kept by force.

The parents have remained in Chicago. Natalie, who is not under court supervision, is living with a cousin, Kulas said.

Polovchak speaks with his parents each week and has "made his position known that he doesn't want to go back. The parents have accepted the fact that he won't go back voluntarily," the attorney said.

The Polovchak family emigrated from the Ukraine to Chicago in January, 1980, but the father, a janitor, decided to return to the Soviet Union about six months later.

A federal court must determine whether a 13-year-old boy has the right to political asylum or whether he should be returned to his parents. Natalie is considered old enough to make up her own mind.

Oral arguments are scheduled before the Illinois Court of Appeals Wednesday on a suit brought by the parents. They contend the Illinois Juvenile Court Act, which has jurisdiction over the boy, is unconstitutionally vague.