The study is scheduled to be released to the U.S. Congress and the public this week.

A U.S. official said that in more than 600,000 documents seized after the 2003 invasion none showed a "direct operational link" between the Iraqi regime and bin Laden' title='Osama bin Laden' class='tpstyle'>Osama bin Laden.

The Bush administration used allegations of such links as a justification for the invasion. Defense Secretary Donald Rumsfeld claimed in 2002 that there was "bullet-proof" evidence and Secretary of State Colin Powell cited links in his February 2003 speech to the United Nations immediately before the invasion.

The study was done by the Institute for Defense Analyses. Officials told McClatchy that it was completed last year and has been going through a declassification review.