Scientists have reportedly concluded that traces of highly-enriched uranium found in Iran two years ago were from imported equipment rather than Iranian nuclear activities.
The findings, reported by the Washington Post and the Associated Press, appear to support Iran's claim that the bomb-grade uranium entered the country together with the centrifuge parts provided by Pakistan.
The Bush administration has cited the material as evidence that Iran is trying to produce highly enriched uranium needed for nuclear weapons.
The European Union has been negotiating with Iran to halt uranium conversion that can lead to high-grade nuclear fuel for atomic weaponry.
However, the Europeans canceled further talks set for August 31, after Tehran resumed uranium conversion activities earlier this month.
IAEA chief Mohamed ElBaradei is due to issue a formal report on Iran's nuclear activities September 3.