The head of the UN's atomic watchdog urged Iran to engage constructively with a team of inspectors heading to Tehran on Friday, after a damning report on Iran's nuclear programme.

Speaking on the sidelines of the Davos forum, International Atomic Energy Agency chief Yukiya Amano told AFP that the organisation's previous efforts to verify whether all its activities were for non-military purposes had been hampered by "a lack of cooperation" from Iran which he hoped would change.

"The high-level team leaves today and starts work tomorrow," Amano said.

"We hope they (Iran) will take a constructive approach. We hope that there will be substantial cooperation."

A report by the IAEA in November highlighted a range of areas which had raised suspicions that Iran was pursuing nuclear weapons, despite its repeated denials.

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.

Amano said it was too early to say definitively that Iran was pursuing a nuclear weapons programme.

But he added: "We have information that indicates that Iran has engaged in activities relevant to the development of a nuclear explosive device."

"We are requesting that Iran clarifies the situation. We proposed to make a mission and they agreed to accept the mission.

"The preparations have gone well but we need to see what actually happens when the mission arrives."

Speaking to reporters earlier, UN chief Ban Ki-moon said that the onus was on Iran to prove its good intentions.

"There is no other alternative to addressing this crisis than peaceful resolution through dialogue," Ban said in Davos.

Iran's President Mahmoud Ahmadinejad has insisted that Tehran is not dodging negotiations and was ready to sit down with world powers -- Britain China, France, Russia, the United States, and Germany for talks.

The six world powers are waiting for Tehran to reply to an October letter sent by EU foreign policy chief Catherine Ashton that stresses that discussions should focus on the "key question" of the Iranian nuclear issue.

Previous talks held a year ago in Istanbul ended without progress.

"Iran should comply with the relevant Security Council resolutions. They have to prove themselves, that their nuclear development programme is genuinely for peaceful purposes which they have not done yet," Ban said.