"Regrettably, the Agency has not been able to make substantive progress on the alleged studies and associated questions relevant to possible military dimensions to Iran's nuclear program. These remain of serious concern," said Mohamed ElBaradei, the head of the International Atomic Energy Agency (IAEA).
He said Iran had so far produced only limited quantities of low enriched uranium, and "this is still a cause for concern for the international community in the absence of full clarity about Iran's past and present nuclear program."
He said the agency "does not in any way seek to 'pry' into Iran's conventional or missile-related military activities. Our focus is clearly on nuclear material and activities. We need, however, to make use of all relevant information to be able to confirm that no nuclear material is being used for nuclear weapons purposes."
ElBaradei urged Iran to show full transparency and implement all measures required "to build confidence in the exclusively peaceful nature of its nuclear program at the earliest possible date."
The next meeting of the so-called Iran Six (Russia, China, the U.S., France, the U.K., and Germany) will be held on Thursday, the French Foreign Ministry said.
Russia has urged Iran to comply with all UN Security Council resolutions and UN nuclear watchdog rulings on its nuclear program.
Moscow has been Tehran's main backer in its civil nuclear power program, and has almost completed Iran's first nuclear plant, in Bushehr.
Iranian President Mahmoud Ahmadinejad said on Thursday his country was undaunted by the possibility of new UN sanctions over its ongoing nuclear program.
France and Britain called for new UN sanctions against Iran following the recent IAEA report. The United States earlier issued a similar call for new sanctions against Tehran.
The Islamic Republic is currently under three sets of relatively mild UN Security Council sanctions for defying demands to halt uranium enrichment.
An IAEA recent report said Iran had not halted its uranium enrichment program and had increased the number of its uranium enrichment centrifuges from 3,300 to 3,820, and that work was under way to install another 2,000 at the Natanz enrichment plant.
The European Union's foreign policy chief Javier Solana said on Thursday that at a Paris meeting of EU foreign ministers the IAEA report "isn't good for Iran," because it indicates that Iran has blocked efforts to investigate its nuclear program.
The IAEA wants Iran to clarify the suspected links between uranium enrichment and tests of high explosives and missile technology allegedly being developed by Iranian scientists by granting access to sites, documents and the relevant officials.
