A retired U.S. Army sergeant described as the key member of a spy ring that compromised vital secrets to the Soviets could face a prison sentence of 10 years to life if convicted of betraying Western defense plans, authorities said Friday.

While it is too early to assess the impact of the spy ring that passed secrets to Moscow, some experts are comparing it to the Walker family spy scandal of 1985, one of the most damaging espionage cases in U.S. history.Authorities said if retired Sgt. Clyde Lee Conrad is convicted on an espionage charge, the sentence could be as high as 10 years, but if he is tried on the more serious charge of treason he could get life.

Officials said Thursday the latest spy ring, led by a retired U.S. Army sergeant who recruited another active duty American soldier, fed NATO and U.S. plans for the defense of Western Europe to Hungarian agents, who passed the secrets on to the Soviet Union.

The ring reportedly included at least eight people in West Germany and Sweden.

The West German newspaper Bild reported Friday that Conrad, a 20-year army veteran who retired in September 1985, repeatedly had received huge payments for his work.

Bild quoted an unidentified West German counterintelligence official as saying the huge sums allegedly paid Conrad indicated the value of his information. It said Conrad received about 2 million marks, or $1,080,000.

"We seldom have had a case where an agent collected millions," he said. "He must have betrayed extremely important secrets."

Conrad allegedly paid another American soldier he recruited as a spy sums of between $5,400 and $54,000, the newspaper said.

"He could not have done it on his pension," a security official was quoted as saying by Bild, which said Conrad's home is modest but luxuriously furnished.

The State Department and the Pentagon refused to comment on the case Thursday, but one U.S. intelligence official in Washington said, "It's an ongoing investigation and extremely sensitive . . . involving information classified at a high level."

While intelligence sources in Washington warned it was too early to assess the impact of the ring's activities, they noted that some military experts were comparing its impact to the Walker case.

Former U.S. Navy Warrant Officer John Walker Jr. sold vital documents and information on secret military codes to the Soviets for 16 years, recruiting his brother, son and a Navy colleague to obtain documents after he retired.

West German government spokesman Norbert Schaefer declined Friday to specifically comment on the spy ring. He said at a Bonn news conference he knew of no other arrests in West Germany except for Conrad and added that that was in the hands of the federal prosecutor.

Schaefer said information on any arrests in other countries would have to come from them.

West German federal prosecutor Kurt Rebmann said officials in Karlsruhe arrested suspects in the latest case on Tuesday, including Conrad, who had access to secret documents and defense plans for seven years.

In Sweden, Goteborg Chief Prosecutor Sven-Olof Hakansson told a news conference that two Hungarian-born brothers who were naturalized Swedes, both of them doctors, were arrested and charged with acting as couriers for Conrad on vacation trips to Hungary.

The wife of one of the brothers was also detained. She was later released but was told not to leave the country.

Hakansson said the brothers, who were not identified, received instructions from West Germany by short-wave radio and transported secret information from meeting places in Western Europe to Hungary. Police confiscated short-wave radios, codes and materials written in Hungarian when they arrested the brothers.

In Washington, the Justice Department said Conrad, 51, has lived in West Germany since retiring from the Army in September 1985.

For the seven years before his retirement in 1985, Conrad was "the custodian of secret matters" in Bad Kreuznach, 40 miles southwest of Frankfurt, Rebmann said. "In this capacity he had access to secret military plans, especially including defense plans."

"After he left the army he attempted to recruit agents for his contact," Rebmann said. "He recruited another member of the U.S. Army for espionage and paid him a sum in five figures for military documents."

At his last meeting with his East Bloc contact, which took place in Vienna last month, Conrad delivered documents in return for money, Rebmann said. He was arrested Tuesday after an extensive investigation by U.S. security authorities and West German counterintelligence agents, Rebmann said.