The State Department yesterday dismissed as "without foundation" a report suggesting that a Ukrainian seaman who jumped from a Soviet ship near New Orleans in October might not have been the same man who later told U.S. officials that he wanted to return home.

The New York Times report, published Sunday, recounted speculation of a possible Soviet-engineered switch that has circulated for weeks in conservative congressional circles and Ukrainian emigre groups concerning seaman Miroslav Medvid.

"The allegations that the Soviets pulled a switch and that a substitute was interviewed is without foundation," said State Department spokesman Charles Redman. "The articles reporting on that have dwelt on some sensational allegations and some unproved theories. They've ignored or misrepresented key facts which make it completely clear that no substitution occurred."

James Lucier, an aide to Sen. Jesse Helms (R-N.C.), who has taken the lead in criticizing official handling of the case, said 60 senators have signed a resolution calling for a special committee to investigate the matter.

Redman, and other department officials who spoke on condition they not be identified, offered a point-by-point refutation of the allegations.

In particular, they said, there was a "reliable chain of government eyewitnesses" who observed Medvid from the time he came ashore on Oct. 24, apparently seeking asylum, through subsequent interviews until Oct. 29 when he signed a statement saying he wished to return home. They said the collective testimony of these witnesses left no doubt that U.S. officials were dealing with the same man.

In addition, they said the Immigration and Naturalization Service took a full-face color photograph of Medvid on Oct. 24. A State Department official who interviewed the seaman after he had been returned to his ship used the photo for identification and to check the information in Medvid's passport.

An immigration officer who was with Medvid on the ship Oct. 25 noticed that he had a callus on his left foot. The man who was interviewed a day later had an identical callus, the officials said.