On the brink of war, both supporters and critics of United States policy on Iraq agree on the origins, at least, of the haunted relations that have brought us to this pass: America's dealings with Saddam Hussein, justifiable or not, began some two decades ago with its shadowy, expedient support of his regime in the Iraq-Iran war of the 1980's.

Both sides are mistaken. Washington's policy traces an even longer, more shrouded and fateful history. Forty years ago, the Central Intelligence Agency, under President John F. Kennedy, conducted its own regime change in Baghdad, carried out in collaboration with Saddam Hussein.

The Iraqi leader seen as a grave threat in 1963 was Abdel Karim Kassem, a general who five years earlier had deposed the Western-allied Iraqi monarchy. Washington's role in the coup went unreported at the time and has been little noted since. America's anti-Kassem intrigue has been widely substantiated, however, in disclosures by the Senate Committee on Intelligence and in the work of journalists and historians like David Wise, an authority on the C.I.A.

From 1958 to 1960, despite Kassem's harsh repression, the Eisenhower administration abided him as a counter to Washington's Arab nemesis of the era, Gamal Abdel Nasser of Egypt -- much as Ronald Reagan and George H. W. Bush would aid Saddam Hussein in the 1980's against the common foe of Iran. By 1961, the Kassem regime had grown more assertive. Seeking new arms rivaling Israel's arsenal, threatening Western oil interests, resuming his country's old quarrel with Kuwait, talking openly of challenging the dominance of America in the Middle East -- all steps Saddam Hussein was to repeat in some form -- Kassem was regarded by Washington as a dangerous leader who must be removed.