Mohammed ElBaradei said that while Iran has made some progress regarding its August deal with the international community, the International Atomic Energy Agency still requires further information on the country's ongoing nuclear programs, The New York Times said.
"The agency has not so far been able to verify some important aspects of Iran's nuclear program," ElBaradei said.
The U.N. official said those aspects include Iran's centrifuge enrichment activities and any ongoing nuclear programs with military implications.
A recent signer of the Non-Proliferation Treaty, Iran has pledged to focus its nuclear efforts on electricity production, not weapons development.
Yet some in the international community, such as the United States, have remained wary of Iran's nuclear efforts and have expressed concern that the Middle Eastern nation is attempting to enrich uranium.
The Times said enriched uranium can be used to fuel nuclear weapons or in powerful nuclear power plants.