Iraqi scientists never revived their long-dead nuclear bomb program, and in fact lied to Saddam Hussein about how much progress they were making before U.S.-led attacks shut the operation down for good in 1991, Iraqi physicists say.

Before that first Gulf War, the chief of the weapons program resorted to "blatant exaggeration" in telling Iraq's president how much bomb material was being produced, key scientist Imad Khadduri writes in a new book.

Other leading physicists, in Baghdad interviews, said the hope for an Iraqi atomic bomb was never realistic. "It was all like building sand castles," said Abdel Mehdi Talib, Baghdad University's dean of sciences.

Seven months after a U.S.-British invasion toppled Saddam's Baath Party government, Iraqi scientists have grown more vocal in countering Bush administration claims, used to justify the war, that Baghdad had "reconstituted" nuclear weapons development, and that it once was a mere six months from making a bomb.

At best, Khadduri writes, it would have taken Iraq several years to build a nuclear weapon if the 1991 war and subsequent U.N. inspections had not intervened.

Dr. Khidhir Hamza was educated in the United States, then was deceptively persuaded to return to Iraq by Saddam Hussein, where for over 20 years he was forced to work at developing an atomic weapon. In 1994, he defected to the U.S. Embassy in Hungary. Dr. Hamza now works as a consultant to the U.S. Department of Energy, and is the author of "Saddam's Bomb Maker: The Terrifying Inside Story of the Iraqi Nuclear and Biological Weapons Agenda."

Afterward, this odd, portly pair -- Perle the Washington insider, Hamza the former paladin of Saddam's palace -- get down to the details. They delight in swapping the latest intelligence about how Iraq may have modified aluminum tubes to enrich uranium.

An Iraqi military defector identified as unreliable by the Defense Intelligence Agency provided some of the information that went into United States intelligence estimates that Iraq had stockpiles of biological weapons at the time of the American invasion last March, senior government officials said Friday.

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Intelligence officers from the D.I.A. interviewed the defector twice in early 2002 and circulated reports based on those debriefings. They concluded he had no firsthand information and might have been coached by the Iraqi National Congress, the officials said. That group, headed by Ahmad Chalabi, who had close ties to the Pentagon and Vice President Dick Cheney, had introduced the defector to American intelligence, the officials said.