Although it received only mild press attention, a March 6, 2003 report by the UN nuclear inspectors cast serious doubt of the existence and extent of a then current Iraqi nuclear program. It later transpired that incriminating documents had been forged to deceive the US public, particularly concerning Iraqi acquisition of uranium (see Yellowcake Forgery).
Many opponents of the invasion also contended that some or all of the weapons inspectors' reports were vastly misrepresented by the Bush administration, especially in the connection between Iraq and terrorist groups.
http://en.wikipedia.org/wiki/Iraq_disarmament_crisis