Marine Corps officials yesterday confirmed that convicted spy Clayton Lonetree's 30-year sentence was reduced by five years in exchange for cooperation with U.S. counterintelligence agents.

Chief Warrant Officer Randy Gaddo added that Sgt. Lonetree, the only Marine ever convicted of espionage, was granted immunity from further prosecution by the commander of the Quantico Marine base where he has been incarcerated for more than nine months.

"A debriefing is being conducted by counterintelligence specialists in an effort to learn of possible damage to the national security and the recruitment methods of hostile intelligence services," Gaddo said.

Lonetree's Minneapolis lawyer, Lawrence Cohen, said yesterday that Central Intelligence Agency and Naval Investigative Service agents have been conducting the debriefing at Lonetree's request "so he could tell his side."

Lonetree, of St. Paul, Minn., was arrested last winter while a guard at the U.S. Embassy in Moscow on charges he passed sensitive information, including detailed floor plans of the embassy, to a KGB agent in exchange for sex with a Soviet woman.

The Moscow "sex-for-secrets scandal" led to the recall in April of the entire 28-Marine guard contingent at the U.S. Embassy. Lonetree was the only Marine found guilty of espionage in the scandal. He was convicted Aug. 21, following a court-martial that lasted more than a month.

"In return for Sgt. Lonetree's cooperation, {base commander Lt. Gen. Frank Petersen} has agreed to reduce his sentence to confinement by five years and to notify the Naval Clemency and Parole Board of the extent and nature of his cooperation," Gaddo said.

Cohen said the decree was issued within the last month and that even further reductions in his client's sentence may occur as the debriefing draws to a close.

Cohen said he believed the reduced sentence would also result in a reduction of Lonetree's current eligibility for parole in 10 years. Gaddo said a review would have to be conducted by the parole board.