Iran acknowledged on Friday that it still has differences with the UN atomic watchdog after two days of talks over its disputed nuclear activities, but also said that the negotiations are progressing.

"Some of the differences were solved but it is very complex issue. ... No agreement has been signed but the negotiations are progressing," Ali Asghar Soltanieh, Iran's envoy to the International Atomic Energy Agency, said on television.

"We hope that they take our considerations into the document; it is a good opportunity to reach an agreement," he said of a "structured approach" deal that would see Iran answer allegations of a military dimension to its nuclear drive.

Tehran denies working on or ever having worked on the bomb and says the IAEA's information is based on faulty foreign intelligence.

Soltanieh's comments came a day after a team led by IAEA chief inspector Herman Nackaerts wrapped up two days of crunch talks in Tehran.

"We decided to have more talks," Soltanieh said after what he called "serious and intensive" negotiations. "When we agree on everything, we will sign it and we let people know the content of the deal."

Nackaerts said in Vienna on Friday that "differences remain so we could not finalize the structured approach to resolve the outstanding issues regarding possible military dimensions of Iran's nuclear program."

The only agreement was for both sides to meet again in Tehran on February 12.