"Based on thorough analysis, the IAEA has concluded ... that these documents, which formed the basis for the reports of recent uranium transactions between Iraq and Niger, are in fact not authentic," International Atomic Energy Agency chief Mohamed ElBaradei said in a report to the U.N. Security Council.
"We have therefore concluded that these specific allegations are unfounded," he said.
Britain and the United States have alleged that Iraq had tried to revive an ambitious atomic weapons program that was neutralized by the United Nations before inspectors left in December 1998.
The claim Iraq had attempted to import the uranium was vital to the U.S. accusation, since it would not have needed the uranium for anything other than a nuclear weapons program.
"After three months of intrusive inspections, we have to date found no evidence or plausible indication of the revival of a nuclear weapons program in Iraq," he said.
To date, the IAEA's inspectors have carried out 218 inspections at 141 sites, he said.
ElBaradei also said extensive investigations of high-strength aluminum tubes Iraq attempted to purchase had confirmed that they were not suitable for a uranium enrichment centrifuge program, as the United States had alleged.
Weakening another U.S. allegation, Elbaradei said IAEA experts had concluded that none of Iraq's declared high-strength magnets could be used directly to enrich uranium for nuclear weapons.
But, ElBaradei added: "Iraq possesses the expertise to manufacture high-strength permanent magnets suitable for use in enrichment centrifuges."
For this reason, the IAEA would continue to investigate and monitor equipment and materials that could be used to enrich uranium, he said.
Baghdad has consistently denied it had attempted to revive its nuclear weapons program.
Like fellow chief U.N. weapons inspector Hans Blix, in charge of the hunt for Iraq's chemical, biological and ballistic weapons, ElBaradei said his agency may interview Iraqi scientists outside Iraq to ensure maximum cooperation.
"We are also asking other states to enable us to conduct interviews with former Iraqi scientists that now reside in those states," ElBaradei said.
The chief nuclear inspector also echoed Blix by saying Iraq had become more cooperative in recent weeks.
"I do hope that Iraq will continue to expand the scope and accelerate the pace of its cooperation," ElBaradei said.