CIA Director George J. Tenet announced yesterday that he has suspended the security clearance of his predecessor, John M. Deutch, for violating government rules by working with classified material on an unsecured computer at his home.

The unprecedented action against a widely respected and still powerful former official comes at a time of heightened concern over foreign espionage and the handling of classified information. It was clearly intended as a signal that the federal government, and the CIA in particular, is determined to tighten security.

Tenet said in a one-page statement that he decided to suspend Deutch's clearance for an indefinite period "upon consideration of the nature of the security violations involved and Dr. Deutch's responsibility, as leader of the Intelligence Community, to set the highest standards in the protection of classified information."

Deutch, who served as CIA director from May 1995 to December 1996 and now teaches at the Massachusetts Institute of Technology, issued a one-page statement of his own, noting that he has served every president since John F. Kennedy in sensitive positions without ever improperly disclosing classified information. But he admitted that his record has not been "free of error."

"While serving as Director of Central Intelligence I erred in using CIA-issued computers that were not configured for classified work to compose classified documents and memoranda," Deutch said. "While it was absolutely necessary for me to work at home and while on travel, in hindsight it is clear that I should have insisted that I be provided the means of accomplishing this work in a manner fully consistent with all the security rules."

Deutch said he "respected" Tenet's decision to suspend his CIA clearances and would do everything he could to assure his former colleagues at the CIA that he is committed to following security rules.

The Justice Department decided in April not to prosecute Deutch for the security lapses, which were discovered when he left office, when CIA specialists went to his Washington home to remove a classified computer and safe. They discovered 31 files containing highly sensitive classified information on his personal computer.

In recent weeks, Chinese American groups have questioned the Justice Department's decision. They said the case appeared to show a double standard, since federal prosecutors are still considering whether to bring charges against Wen Ho Lee, a Chinese American physicist at Los Alamos National Laboratory who admitted to keeping secret data on an unclassified computer in his office. Lee has come under suspicion of espionage and was fired from his job as a nuclear weapons designer in March, although he has not been charged with any crime and maintains that he is innocent.

It remains unclear whether Deutch will also lose his Defense Department security clearance, but one high-ranking government official said he believed Tenet's decision would lead to the suspension of all of Deutch's clearances. Tenet has sole discretion in deciding if and when Deutch's CIA clearances can be restored.

The rebuke was all the more striking because Deutch remains an intimate of many of the most senior officials in the Clinton administration's foreign policy team. He is close friends with Deputy Secretary of State Strobe Talbot and remains in regular contact with other senior officials at the White House and intelligence agencies.

Newsweek first reported in April that Deutch was under investigation for mishandling classified information. The investigation languished while Deutch was appointed by the CIA to head a bipartisan commission on weapons of mass destruction. But the probe took on urgency, Newsweek reported, when Energy Secretary Bill Richardson picked Deutch to head an effort to evaluate security problems at the nation's nuclear laboratories, an advisory post from which Deutch quickly withdrew.

Staff writer John F. Harris contributed to this report.