A federal appeals court here was asked yesterday to block temporarily the departure of a Soviet freighter on the Mississippi River until U.S. officials can reinterview a Ukrainian sailor to see if he wants asylum.

Andrew Fylypovych of the Ukrainian-American Bar Association, argued that the government had failed to follow federal immigration law in its handling of the situation, which began Oct. 24 when Miroslav Medvid jumped into the river near New Orleans. Fylypovych said that the ship should be detained until the law is properly carried out.

Fylypovych told a three-judge panel of the U.S. Court of Appeals that Border Patrol agents who interviewed the sailor had not provided Medvid with the forms required in asylum situations and had failed to notify the State Department immediately. Both procedures are required by immigration law, he said.

In addition, Fylypovych said, four days after patrol agents returned Medvid to the Soviet ship, U.S. government officials again failed to follow regulations because they reinterviewed Medvid in the presence of Soviet authorities. During that interview, Medvid said he wanted to return to the Soviet Union.

"The seaman should be left alone without the presence of Soviet officials," said Fylypovych. "When U.S. officials are with Soviet officials at the same time . . . it's inconceivable for him to ask for political asylum."

The appeals court arguments are the latest legal round in the seaman's case. On Friday, U.S. District Court Judge Louis F. Oberdorfer denied Fylypovych's motion for a temporary restraining order preventing the ship from leaving. Oberdorfer said he was not convinced that U.S. officials made an "arbitrary or capricious" decision when they concluded Medvid was voluntarily departing from the United States.

The Soviet grain freighter is scheduled to depart for the Soviet Union on Friday, according to officials. The appeals court is expected to rule before then.

Medvid, 22, who speaks no English, swam ashore in Belle Chasse, La., the night of Oct. 24 and was greeted by a local jeweler and a sheriff. After several hours, he was taken to the Border Patrol, a division of the Immigration and Naturalization Service, in nearby New Orleans, according to his lawyers.

Border Patrol officers telephoned an interpreter, Irene Padoch, who was in New York City. For one hour, Padoch interpreted for Medvid and the Border Patrol officers, Padoch said.

In an affidavit filed in court, Padoch said she told Border Patrol agents that Medvid wanted political asylum. Padoch said she also told agents that Medvid jumped from the ship because "he wanted to live in an honest country."

Assistant U.S. Attorney R. Craig Lawrence argued that "the overriding question is a political question." If the court intervenes, he said, "it could create what amounts to an international incident."

Lawrence said the Soviet freighter should be allowed to leave because Medvid convinced U.S. officials in his second interview that he wanted to go home.

Lawrence also said in an affidavit filed in court after the hearing that the procedure followed during the second interview was in accordance with the law. He did acknowledge that immigration officials may have violated procedures in their first contact with Medvid.

The chief of the Border Patrol, Roger Paul Brandemuehl, told Oberdorfer that he was present for the second interview and was convinced that Medvid wanted to return to the Soviet Union.

Yesterday, three Ohio women hired a launch and approached the Soviet freighter with a letter for its captain. The women said they think Medvid is a relative and asked to speak with him. They were denied permission.