The head of the UN atomic watchdog IAEA said Wednesday he had little hopes of a breakthrough at a meeting later this week with Iran to discuss Tehran's contested nuclear programme.

"I cannot say at this time that I am optimistic about the outcome of the coming meeting," Yukiya Amano, the head of the International Atomic Energy Agency, told AFP during a visit to Helsinki.

Friday's talks are aimed at resolving outstanding issues relating to Iran's nuclear programme and obtaining a "structured approach" agreement to clarify accusations that Iran is carrying out suspected nuclear weapons research.

"We have made our best efforts in a constructive spirit to work out an agreement between Iran and the IAEA but so far we have not been successful in reaching an agreement," he told reporters.

"I do not have the indication that this will be changing very soon," he said, adding that Iran's "level of cooperation is insufficient".

IAEA chief inspector Herman Nackaerts and deputy director general Rafael Grossi were expected to attend the talks at the Iranian mission in Vienna.

In June, the IAEA and Iran failed to agree to a deal allowing greater access to examine Tehran's contested nuclear programme.

Tehran insists its nuclear programme is only for civilian purposes.

Amano said meanwhile that satellite imagery of Iran's Parchin military site suggested Tehran was trying to block verification of the site.

"Until we have access to the facilities we cannot say for sure. But through the satellite imagery we think that Iran is moving soil, demolishing buildings, using water, removing fences, doing landscape activities, etc," he said.

"We are thinking that this would hamper verification activities," he said.

"We are not saying that Iran has some nuclear weapons ... (but) because the pieces of information are indicating activities with possible military dimensions we would like Iran to engage with us to clarify these issues," he said.