Chief weapon hunter Charles Duelfer is expected to make only small additions to his October report that found Saddam Hussein's weapons of mass destruction programs had deteriorated into only hopes and dreams by the time of the U.S.-led invasion in 2003, says White House spokesman Scott McClennan.
The decline in the weapons program was wrought by the first Gulf War and years of international sanctions, the report concluded.
Violence in Iraq and an absence of new information prompted Duelfer's team to return home before Christmas, the Washington Post reports.
Duelfer's findings contradicted nearly all of the assertions by the Bush administration about Iraq's threat in 2002 and early 2003.
What ambitions Saddam harbored for such weapons were secondary to his goal of evading those sanctions, and he wanted them primarily not to attack the United States or to provide them to terrorists, but to oppose his older enemies, Iran and Israel, the report found.
Duelfer's Iraq Survey Group drew on interviews with senior Iraqi officials, 40 million pages of documents and classified intelligence to conclude that Iraq destroyed its undeclared chemical and biological stockpiles under pressure of U.N. sanctions by 1992 and never resumed production.
Iraq ultimately abandoned its biological weapons programs in 1995, largely out of fear they would be discovered and tougher enforcement imposed.
"Indeed, from the mid-1990s, despite evidence of continuing interest in nuclear and chemical weapons, there appears to be a complete absence of discussion or even interest in BW at the presidential level," according to a summary of Duelfer's 1,000-page report.