Marine Sgt. Clayton J. Lonetree was sentenced to 30 years in prison yesterday for spying for the Soviet Union while assigned to guard the U.S. embassies in Moscow and Vienna.

After almost three hours of deliberations, an eight-officer military jury decided against giving the 25-year-old Marine from St. Paul, Minn., the maximum life sentence that the prosecution had demanded. The jury was the same that Friday found Lonetree guilty of espionage and 12-related counts, including conspiracy and failure to report contacts with citizens of a communist-controlled country.

Lonetree's crimes included passing the names of nine Central Intelligence Agency operatives in Vienna to a KGB agent, Alexei Yefimov, while Lonetree was stationed as a Marine guard at the Moscow and Vienna embassies between 1984 and 1986. Yefimov was introduced to Lonetree as Uncle Sasha by Violetta Sanni, a translator at the Moscow Embassy with whom Lonetree had an affair.

Lonetree, the first marine convicted of espionage, told the jurors prior to their deliberations that he "was not going to blame anyone" and said he was "willing to accept any punishment the court could offer."

However, "I think they should look into a person's background," he told the jurors.

"Since the start of the Marine Corps, marines have served with honor and died with honor. But only one marine has made the decision to betray his oath, his corps and his country," prosecutor Maj. Frank Short told the jury.

"A single incident of espionage carries the potential for a life term. Here you see a broad, sweeping course of conduct {which took place} in two different embassies, involving two chief directorates of the KGB, three coconspirators and a dozen meetings," said Short.

"He betrayed people by including them on a KGB target list for reasons of his own lust and selfishness," he said.

Short asked for a life sentence that he said "fits the crime and fits the criminal."

But defense lawyer Michael Stuhff told the jury that State Department policies played a major role in Lonetree's problems.

Marine guard duty was "difficult enough for a young man without the State Department deliberately and recklessly throwing out temptation . . . at Marine balls, when the State Department invites attractive foreign nationals to the Marine House." Lonetree danced with Sanni at a Marine ball.

The nonfraternization was "as difficult to enforce as a regulation forbidding salmon to swim upstream," said Stuhff.

The honor of the Marine Corps was besmirched not by Lonetree but by Navy Investigative Service exaggerations, by the State Department and others, he said.

Maj. David Henderson, a military member of Lonetree's defense team, suggested a 10-year sentence.

The jury also reduced Lonetree's rank to private, fined him $5,000 and gave him a dishonrable discharge. Lonetree will be eligible for parole in 10 years, less the 236 days he has already spent in confinement.

Had he received the maximum life sentence, he would also have been eligible for parole in 10 years.

"I think they wanted to do less than life but still sock it to him," defense attorney William Kunstler said after the sentencing.

"This is not any sort of victory. It's still a kick in the teeth. {The jury} knew they were doing a bad thing. To make it palatable they gave less than the prosecution asked for," said Kunstler, who last week predicted Lonetree would be sentenced to life.

Defense attorneys said they would appeal, arguing that rulings by military judge Navy Capt. Philip F. Roberts prevented them from presenting an adequate defense.

Lonetree's sentence appears light in comparison to some sentences in recent espionage trials.

Jerry A. Whitworth, a member of the infamous Walker family spy ring, was sentenced last August to 365 years in prison and fined $410,000 for his role in funneling Navy secrets to the Soviet Union. Whitworth, 48, will have to serve 60 years before being eligible for parole.

John Anthony Walker Jr., the leader of the ring, was sentenced Nov. 6 to life in prison under a plea bargain agreement that gave his son, Michael, another member of the ring, a 25-year sentence.

Jonathan J. Pollard, a naval intelligence analyst who was accused of spying for Israel, also was sentenced last year to life in prison and Ronald W. Pelton, a former National Security Agency employe, received three life sentences plus 10 years for selling secrets to the Soviets. Staff writer Bill McAllister contributed to this report.