Iran has produced about seven tons of a gaseous compound that can be used for uranium enrichment since it restarted that process last month, the International Atomic Energy Agency reported Friday. A former U.N. nuclear inspector said the quantity of uranium hexafluoride would be enough for an atomic weapon.

The IAEA report said that questions remain about key aspects of Iran's 18 years of clandestine nuclear activity and that it still was unable "to conclude that there are no undeclared nuclear materials or activities in Iran."

"Iran's full transparency is indispensable and overdue," said the document, obtained by a number of news organizations. The document listed perceived Iranian failings and called for "access to individuals, documentation related to procurement . . . certain military-owned workshops and research and development locations."

Among the unanswered questions, according to the report, were gaps in the documented development of Iran's centrifuge program used in uranium enrichment -- and in what was received, and when, from the black market network headed by the Pakistani scientist Abdul Qadeer Khan.

Overall, the report confirmed recent revelations that most of the traces of weapons-grade uranium found in Iran were imported on equipment from Pakistan that was bought on the black market -- although it said it was not possible to determine the origins of other traces enriched to a lesser grade.

That finding hurts U.S. arguments that the traces were likely the result of enrichment conducted in Iran as part of a secret program to make nuclear weapons.

But the key issue in the report was uranium conversion -- changing raw uranium into gas that then is spun by centrifuges into enriched uranium.

The report, prepared by the head of the IAEA, Mohamed ElBaradei, said Iran had produced about 15,000 pounds of uranium hexafluoride, the gaseous compound that is converted into enriched uranium. Depending on the level of enrichment, that substance can be used either as a source of power or as the core of a nuclear weapon.

The document did not indicate whether Iran was pursuing a nuclear weapon, and Tehran insists that it intends only to generate nuclear power for peaceful purposes.

David Albright, a former IAEA nuclear inspector, said that if Tehran used the material for weapons purposes, it would be enough for one atomic bomb.