Accurate CIA judgments of the risks involved with U.S. military intervention in Vietnam fell victim to political pressure within the Kennedy and Johnson administrations, a newly declassified CIA study concludes.

Written by Harold Ford, author of many of the spy agency's classified estimates on Vietnam at the time of the war, the study shows how executive branch pressure effectively tamped down the warnings coming from mid-level CIA analysts and field operatives.The study, "CIA and the Vietnam Policymakers," largely confirms long-established historical views about the agency's role in Vietnam but adds new detail through the author's access to classified agency files.

"CIA's judgments proved prescient much of the time but found little receptivity," wrote Ford, who worked under the auspices of the CIA's Center for the Study of Intelligence. "At other times during 1962-68, the agency's intelligence found favor with policymakers but turned out to be wrong. Despite this mixed performance . . . the intelligence on Vietnam that the agency provided decisionmakers was for the most part better than that of other official contributors."

Stanley Karnow, author of a history of Vietnam, said at a Georgetown University seminar Tuesday that, in his experience, CIA analysts "were professionals who tried to assess a situation as they saw it and not try to fit it in with any policy position." Chester Cooper, who worked on Vietnam issues in the Johnson White House, called the study "impeccable and very candidly researched."

Thomas Hughes, former head of the State Department's intelligence bureau, while praising the book, said it discounted the equally accurate assessments of Vietnam coming from State's intelligence analysts.

The study deals with intelligence concerning three phases of the war: the period during the Kennedy administration when the debate raged in the White House as to whether South Vietnam could defend itself; the period leading up to President Johnson's 1965 decision to bomb North Vietnam and dispatch U.S. ground forces; and the months preceding the January 1968 Tet offensive that shook U.S. support for continuing the war.

A draft of a 1963 National Intelligence Estimate, "NIE 53-63," predicted that "The struggle in South Vietnam at best will be protracted and costly (because) very great weaknesses remain and will be difficult to surmount." After senior policy-makers and military officers objected to this pessimistic outlook, and after then-CIA Director John McCone demanded a redraft, the final version stated: "We believe that Communist progress has been blunted and that the situation is improving."

During one internal meeting, McCone upbraided the CIA's chief analyst, Sherman Kent, for failing to consult "the people who knew Vietnam best," including diplomats, military officers and others. The end result, Ford writes, was an intelligence estimate that largely echoed the optimistic views of policymakers who had a vested interest in praising the effectiveness of their own actions.