The UN nuclear watchdog has urged Iran to improve co-operation with inspectors investigating its nuclear programme.
The IAEA is optimistic about EU talks with Tehran
The International Atomic Energy Agency (IAEA) endorsed talks between the EU and Tehran over its nuclear activities, at the close of a three-day meeting.
European negotiators want Iran to abandon uranium enrichment in return for trade and security benefits.
The US has accused Iran of secretly trying to develop nuclear weapons - a charge Tehran denies.
However, it has suggested it is considering whether to back the EU initiative.
'Above and beyond'
The IAEA meeting in Vienna ended on Thursday with the board of governors expressing optimism about the outcome of talks between Tehran and Britain, France and Germany.
For the first time since the IAEA began investigating Iran's nuclear programme in February 2003, the governors did not adopt a formal resolution criticising Tehran.
But agency spokesman Mark Gwozdecky told BBC News that Iran needed to improve its openness about its nuclear activities.
He said: "What that means is, because of the many years of concealment of its nuclear programme, Iran needs to go above and beyond the letter of the law, above and beyond its legal obligations in terms of transparency, in order to convince the international community that its programme is peaceful."
At the meeting, the EU and the US criticised Iran for its lack of co-operation and failing to give UN inspectors full access to its nuclear sites.
US ambassador Jackie Sanders told the 35-nation board that "there remains an alarming number of unresolved questions about Iran's nuclear programme".
So far, the US has adopted a confrontational approach, threatening to have Iran referred to the UN Security Council for possible sanctions.
Talks between the European trio and Iran resume in Geneva next week.
Reports say Washington may support the negotiations by helping Tehran join the World Trade Organisation or modernize its civil aviation fleet.