The UN atomic watchdog IAEA said Wednesday it would hold new talks in Tehran this month, as its chief inspector returned from Iran warning there was "still a lot of work to do" on its nuclear programme.

The International Atomic Energy Agency said in a statement that another meeting would take place in Tehran from February 21 to 22, adding that it was committed to "intensifying dialogue".

Earlier, chief UN nuclear inspector Herman Nackaerts told reporters on his return from a three-day trip to Tehran that his six-member team had had a "good" visit.

The trip, which according to Tehran did not take in any atomic sites, was organised in the wake of a damning IAEA report on Iran's nuclear ambitions issued in November.

"We had three days of intensive discussions about all our priorities. We are committed to resolving all the outstanding issues and the Iranians said they are committed too," Nackaerts said at Vienna airport.

"But of course there is still a lot of work to be done, and so we have planned another trip in the very near future."

The visit took place against a backdrop of heightened tensions following the November IAEA report that significantly raised suspicions Iran had done work on developing nuclear weapons.

The United States, the European Union and others have since ramped up sanctions to target Iran's oil industry and central bank. Tehran has threatened to close the Strait of Hormuz, a chokepoint for global crude shipments.

"The agency is committed to intensifying dialogue. It remains essential to make progress on substantive issues," IAEA Director General Yukiya Amano said in a statement as the agency announced the new dates for talks.

Iranian Foreign Minister Ali Akbar Salehi told the Fars news agency that the IAEA talks were "good" and that it was agreed to continue them in the future.

"The delegation had some questions about the alleged studies (in the November report), and thanks to God we had very good sessions," he was quoted as saying.

"They did not visit any nuclear sites. We were ready to facilitate such visits if they had wanted to."

The IAEA, which has refused to give any details about the visit, only said Wednesday that it had "explained its concerns and identified its priorities, which focus on the clarification of possible military dimensions to Iran's nuclear programme."

"The IAEA also discussed with Iran the topics and initial steps to be taken, as well as associated modalities," it said.

"The key question for us in evaluating whether it was a good visit is, did Iran offer any cooperation on substance?" a Western diplomat in Vienna told AFP.

"We hope to hear from the IAEA very soon whether any substantive questions were addressed during the visit."

Nackaerts had said before leaving that dialogue with Iran was long overdue.

In its November report, the IAEA said it had a trove of evidence that "indicates that Iran has carried out activities relevant to the development of a nuclear device."

It detailed 12 suspicious areas such as testing explosives in a steel container at a military base and studies on Shahab-3 ballistic missile warheads that the IAEA said were "highly relevant to a nuclear weapon programme."

Iran insists its nuclear drive is for peaceful purposes and that the IAEA report was based on "forgeries" provided by its enemies.

But the agency says Iran has a long history of being in breach of its obligations to declare nuclear facilities and materials and that it is unable to conclude all Tehran's activities are peaceful.

The last full talks between Iran and the so-called P5+1 -- the US, China, Russia, Britain, France and Germany -- broke down a year ago in Turkey, although Iran's President Mahmoud Ahmadinejad has insisted Tehran is ready to sit down with world powers.

The IAEA said in January that Iran had begun enriching uranium to 20-percent purity deep inside a mountain bunker at Fordo, taking it significantly closer to the 90-percent mark needed for a nuclear bomb, even as it vowed to keep up cooperation with the IAEA.

Top US intelligence officials suggested Tuesday that military conflict with Iran was not inevitable, despite the soaring tensions, and that sanctions and diplomacy could still succeed in persuading Tehran to cooperate.

US President Barack Obama in his State of the Union address last week noted that "a peaceful resolution" remained possible.