MOSCOW - Russia's spy service said Wednesday that granting U.S. citizenship to a former KGB general is proof that he betrayed Russia.

Retired Gen. Oleg Kalugin, who ran the KGB's counterintelligence department from 1973 to 1980, received U.S. citizenship earlier this week. He has been critical of his former agency since retiring in 1990 and has been living in the United States for years.

Boris Labusov, a spokesman for the Russian Foreign Intelligence Service, a top KGB successor agency, said that Kalugin could only become a U.S. citizen if he provided in-depth information about his KGB activities to the U.S. authorities.

"A person seeking U.S. citizenship must prove that he carries no threat," Labusov said in a telephone interview. "The only way for a former intelligence officer to do that would be telling honestly about his work for the Soviet intelligence service."

In June 2002, the Moscow City Court convicted Kalugin of treason and sentenced him to 15 years during an in-absentia trial that was conducted hastily before such trials were prohibited by new Russian law.

The court found Kalugin guilty of giving away state secrets in his U.S.-published book "The First Directorate" that described his 22-year KGB career and included information about Americans who worked as Soviet agents.

Kalugin said his book gave only a "general description" of events during his career at the KGB. He said that the court had failed to prove his guilt and described the trial as an act of revenge by his former colleagues - one of whom is President Vladimir Putin, also an ex-KGB agent.

Putin has publicly called Kalugin a "traitor," and Kalugin has said he has no intention of returning to Russia as long as Putin is in power.

Kalugin has parlayed his notoriety into a lucrative source of income: working as a consultant for U.S. companies, creating a computer spy game with former CIA head William Colby and even giving espionage tours around Washington with a former American spy.