The Central Intelligence Agency -- under fire for its recent handling of Vitaly Yurchenko's "defection" from the Soviet intelligence service -- broke its official silence last night by issuing an unusual three-page statement detailing Yurchenko's life and describing him as a man "whose relationship with his wife was seriously strained prior to his defection."

The biography, which described Yurchenko as a "general-designate" in the KGB with 25 years' experience, was issued late in the day to news services in Washington without explanation or comment.

The CIA statement said that from April to July this year, Yurchenko's duties included supervising the selection of KGB agents in the United States and KGB joint operations with the spy services of other communist countries. He had direct authority over "KGB residents" in Canada and coordinated spy "work against American citizens."

According to the CIA statement, Yurchenko also supervised wartime contingency planning for the KGB in North America, including "selecting agents to be used after the beginning of war; and working out agent communications plans."

CIA spokeswoman Patti Volz -- who two days ago said, "The CIA has never commented about Yurchenko. We don't talk about defectors" -- last night said the biography was issued because "people were asking for it and it was decided to make it available to certain individuals."

An intelligence community official said last night that one explanation for the statement was that the CIA has been smarting over assertions in the news media that Yurchenko was not the "big fish" the CIA has claimed in private briefings on Capitol Hill.

CIA officials have consistently described Yurchenko as a high-ranking KGB officer, and some intelligence sources have been quoted saying he was as high as No. 5 in the Soviet secret police.

In a highly embarrassing episode for the CIA, Yurchenko walked out of a Georgetown restaurant last Saturday night and ended his three-month defection by walking into the Soviet Embassy compound in upper Northwest Washington. There he called an extraordinary news conference last Monday evening to accuse the CIA of kidnaping him, drugging him and holding him against his will at a safe-house near Fredericksburg, Va.

The CIA denied Yurchenko's allegations and has told Senate and House intelligence oversight committees that the agency will try to sort out whether Yurchenko was a genuine defector or a clever double agent who thoroughly duped U.S. intelligence.

"I am puzzled," said Sen. William S. Cohen (R-Maine) last night. "If this is an attempt to validate his real identity, we will need more."

Added one congressional oversight committee member, "I don't know what this statement proves. This is information they obviously got from him. It doesn't disprove other statements about how high he was."

The biography says Vitaly Sergeyevich Yurchenko was born on May 2, 1936, near the village of Smolensk, the son of a factory worker who died at the siege of Leningrad during World War II and a mother who worked on a collective farm and died in Leningrad earlier this year.

Yurchenko, the statement says, went to military training school and entered the Soviet submarine service, graduating with a degree in navigation in 1958. He was commissioned as a navy lieutenant assigned to the Pacific fleet headquartered in Vladivostok.

Married in 1958 to a woman who works as a engineer at a Moscow construction institute, Yurchenko has a daughter born in 1961 and an adopted son born in 1969. His KGB career reportedly began in 1959, when he joined the KGB third Chief Directorate as a counterintelligence officer in the armed forces. He remained attached to the armed forces during most of the 1960s.

The statement confirmed that Yurchenko worked as the internal security officer at the Soviet Embassy here from 1975 to 1980, when he was transferred to Moscow as a top counterintellignece officer in charge of internal security within the KGB, guarding against leaks and espionage by KGB employes. This office worked with defectors to the Soviet Union, including former British spies, H.A.R. (Kim) Philby and George Blake, the statement said.

Finally, in April of this year, Yruchenko was promoted to be deputy chief of the First Department of the KGB's First Chief Directorate, which supervises intelligence gathering in the United States and Canada. The CIA said Yurchenko personally supervised the KGB staff in Montreal and Ottawa.

Intelligence sources said earlier this week that after his August defection, Yurchenko was clandestinely taken to Ottawa to meet the woman with whom he had been romantically involved and who, Yurchenko hoped, would join him. But the woman reportedly spurned him.