El-Baradei, who is the head of the International Atomic Energy Agency (IAEA), the UN's nuclear watchdog, made the statement in Oslo, one day before he is to receive the Nobel Peace Prize along with the IAEA.
"We have been working with the Iranian authorities to clarify the extent and nature of their [nuclear] program," he said. "The jury is still out because we reconstructed a good part of the puzzle about their clandestine past program, but important pieces are still missing, and I am calling on Iran to be as active, as transparent as possible because the international community, after three years, is losing patience about the nature of that program."
El-Baradei said he hopes outstanding nuclear issues with Iran will be clarified next year. He also encouraged European negotiators to continue talks with Iran.
No date has been set to resume the talks with Britain, France, and Germany -- which broke off in August after Tehran restarted uranium conversion -- a precursor to enrichment.
Separately, condemnation continues to pour in from around the world after Iran's president questioned the existence of the Holocaust and suggested that Israel be moved to Europe.
Iranian President Mahmud Ahmadinejad made his controversial comments on 8 December at an Islamic summit in Saudi Arabia.
Today, 9 December, Germany and Austria summoned Iranian ambassadors to deliver protests about the remarks. The EU and Switzerland also criticized them, while Russia's foreign ministry called the comments "unacceptable."
RFE/RL Iran Report
SUBSCRIBE For regular news and analysis on Iran by e-mail, subscribe to "RFE/RL Iran Report."