The head of the International Atomic Energy Agency (IAEA) is pressing Iran to suspend more of its uranium enrichment programmes.
Mr Mohamed El baradei said a "generous, comprehensive suspension" would be required to create confidence in the international community.
The move would lead to speedier normalisation of relations with the country, he said following talks with Iranian Foreign Minister Mr Kamal Kharrazi at the World Economic Forum in Davos, Switzerland.
He said IAEA concerns focused on the discovery by agency inspectors in Iran of equipment contaminated with highly enriched uranium, along with continued enrichment-related activities like production of centrifuges.
Iran has blamed the contamination on parts imported from elsewhere but have not identifyied their origin.
Asked about the IAEA's concerns, Mr Kharrazi said: "It's just a question of spare parts or something, it's minor issues."
"We have very good cooperation with the IAEA," he said. "I believe the important thing is that we do not have any programme to produce weapons and this is now established." US Vice President Dick Cheney, also in Davos, said his country would support European diplomatic efforts to get the Iranians to agree to a more intrusive inspection regime.
"We'll have to see whether or not that produces the desired result. We believe the Iranians have been actively and aggressively pursuing an effort to develop nuclear weapons," Mr Cheney told the conference of political and business leaders.