Shortly after the failed Bay of Pigs invasion of Cuba in 1961, a top CIA official told an investigative commission that the Soviet Union had somehow learned the exact date of the amphibious landing in advance, according to a newly declassified version of the commission's final report.

Moreover, the CIA apparently had known of the leak to the Soviets--and went ahead with the invasion anyway.

In an effort to oust Fidel Castro, the CIA organized and trained a force of about 1,400 Cuban exiles and launched the invasion on April 17, 1961. Castro's soldiers easily repelled the landing force in less than 72 hours, killing 200 rebels and capturing 1,197 others in what became one of the worst foreign policy blunders of the Cold War.

The investigative commission, chaired by Gen. Maxwell Taylor, was established almost immediately and held a series of secret hearings at the Pentagon before sending a sharply critical report to President Kennedy in June 1961.

While portions of the Taylor Commission's report were made public on two previous occasions, in 1977 and 1986, many pages had been blacked out for security reasons by the CIA. The newly declassified version, in contrast, is nearly free of deletions and contains a wealth of new detail.

The National Archives released the document late Wednesday to the nonprofit National Security Archive, where senior analyst Peter Kornbluh has been working for years to prod the government to release all classified documents on the Bay of Pigs.

Kornbluh began demanding the full version of the Taylor Commission report in December after determining that the document, cleared for release by the CIA in 1996, had been lost by Pentagon officials.

"This document represents a case study of bureaucratic laxity when it comes to the declassification of important history," Kornbluh said yesterday. "I was told by the Kennedy Library [in December] that the Taylor report was sitting at the Pentagon--and had been for three years at that point."

When Pentagon officials could not locate the document, Kornbluh said, the whole declassification review process involving the CIA, State Department, Pentagon and other intelligence agencies had to be restarted by officials at the National Archives, where the process finally was completed just days ago.

Lt. Col. Catherine Abbott, a Pentagon spokeswoman, blamed the John F. Kennedy Library in Massachusetts for sending the document in 1996 to the Defense Department's Office of General Counsel, rather than to a special declassification office. Abbott said she did not know what happened to the document after it arrived in 1996.

Documents found in Soviet archives previously indicated that the Russians had learned some details of the operation in advance, but the Taylor Commission report shows for the first time that the CIA knew about the leak and proceeded with the invasion nevertheless.

The revelation came in testimony before the Taylor Commission--blacked out in previous releases of the report--by Jacob D. Esterline, the CIA operations official who headed the task force responsible for coordinating the invasion.

"There was some indication that the Soviets somewhere around the 9th [of April] had gotten the date of the 17th," Esterline testified. "But there was no indication at any time that they had any idea where the operation was going to take place."

How the leak occurred is still a mystery.

In extremely candid testimony, Esterline called Tony Varona, one of two Cuban exile leaders working closely with the agency, "an ignoramus of the worst sort" who had "no conception whatsoever of security."

Referring to Varona and his cohorts, Esterline complained, "I've never encountered a group of people that were so incapable of keeping a secret."

For this reason, he explained, CIA planners told none of the Cuban participants when the invasion would actually take place until a briefing on April 12. Since the Soviets had by then already obtained the date, either through a source or a communication intercept, "we were able to isolate the fact that the leak could not have been Cuban," Esterline said.

Kornbluh said there is no indication that Esterline or anyone else at the CIA warned President Kennedy of the leak before the invasion took place.

The newly declassified report also shows that CIA Director Allen W. Dulles expressed doubt just three weeks after the invasion about whether the CIA should have any further involvement in paramilitary operations.

"I'm the first to recognize that I don't think that the CIA should run paramilitary operations of the type in Cuba," Dulles said. "I think we should limit ourselves more to secret intelligence collection and operations of the nonmilitary category."