"We have a very transparent programme and we believe that the problems have been resolved," Gholamreza Aghazadeh, head of Iran's Atomic Energy Organisation told a news conference following Monday's discussions.

Heinonen did not attend the news conference and was due to return to Vienna Monday night. He had arrived in Iran earlier in the day.

However, two members of his staff would remain in Tehran for further discussions with Iranian officials, a source close to the negotiations said.

Earlier, Iran's ambassador to the International Atomic Energy Agency (IAEA), Ali Asghar Soltanieh, was quoted by the FARS news agency as saying the talks, which opened Monday, would probably last three days.

Iran has insisted that Heinonen's visits to Tehran are part of its routine cooperation with the IAEA but the watchdog has said they are focussed on the weapons claims.

Heinonen had held closed-door talks with Iranian officials in Tehran on April 21 and 22.

The IAEA said on Wednesday that Heinonen reached an agreement with Iran to examine the allegations Tehran has studied how to design nuclear weapons. The claims stem from intelligence provided to the IAEA by some member states.

But Iranian officials have repeatedly played down the links between Heinonen's visit and the so-called weaponisation studies. Tehran has not confirmed the existence of the new agreement.

"This session too is like other normal meetings that deal with technical and expert discussions under the framework of the agency's statute and the nuclear Non-Proliferation Treaty," Soltanieh said of the new talks.

"If there are any questions or ambiguities, we will give the necessary answers away from political fuss," said Soltanieh, who is heading the Iranian delegation in the talks.

In a closed-door briefing to diplomats at IAEA headquarters in Vienna on February 25, Heinonen presented detailed information suggesting that Iran could have been studying how to use its nuclear technology to make a warhead.

Iran, which insists its nuclear programme is entirely peaceful and aimed solely at generating energy, furiously denounced the presentation as fake.

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.