The government of West Germany has formally protested to the U.S. State Department the circumstances under which Arthur Rudolph, the designer of the Saturn V moon rocket, returned to Germany last year and renounced his U.S. citizenship.

Rudolph left the United States rather than face allegations by the Justice Department that he "worked thousands of slave laborers to death" while supervising production of V2 missiles for the Nazis during World War II.

Rudolph was one of 118 German rocket scientists, including his close friend Wernher von Braun, who were brought secretly to the United States after World War II to work for the Army and later the National Aeronautics and Space Administration.

After being shown Justice Department evidence, Rudolph left the United States in March 1984 and renounced his citizenship May 25 at the U.S. Consulate in Hamburg.

German Consul General Elfriede G. Kruger said her government informed the State Department that Rudolph "arrived illegally. When somebody has a passport, it means the government will take the bearer back. That didn't happen."

But a State Department official said he believes Rudolph's actions were voluntary and are "consistent with international law." He said that since Rudolph concealed his Nazi past when he applied for U.S. citizenship, an argument could be made that he was never legally a U.S. citizen.

The official said that although there has been no U.S. response yet to the protest, he believes Rudolph will probably not be allowed to return to the United States.

Allan A. Ryan Jr., the former head of the Justice Department Office of Special Investigations, which tracks suspected Nazi war criminals, said, "What the Germans choose to do with Rudolph is up to them. We spent two years investigating the case and proved -- at least to Rudolph's satisfaction -- that he is not someone we want in this country."

The World Jewish Congress charged yesterday that the controversy over Rudolph is part of a "deliberate policy" of the West German government to block deportation of war criminals to West Germany.

The New York-based group released a copy of a 1954 agreement in which the Germans agreed to readmit "any person who has received a visa for the United States under the Refugee Relief Act of 1953 . . . if it subsequently established that such person received the visa through fraud or through misrepresenting material facts."

"We are not aware of such an agreement," Kruger said. She said the original has not been found in the German archives, although she said she has a photocopy.

Ryan said that despite efforts by Justice to invoke the 1954 agreement, "They have been most reluctant to accept back former Nazis."