The UN nuclear agency says talks with Iran on its controversial nuclear programme have been constructive and will continue in the coming weeks.
Olli Heinonen, IAEA deputy head, heads the delegation
The deputy head of the agency, Olli Heinonen, has been in Tehran for two days of discussions with Iran's deputy nuclear negotiator, Javed Vaeedi.
Iran is under pressure from the US and EU to halt uranium enrichment, and the UN has imposed sanctions against it.
Iran says its nuclear programme is for purely civilian purposes.
The UN Security Council has already imposed two rounds of sanctions on Iran for not suspending its uranium enrichment programme, and is now considering a third round.
But Iranian President Mahmoud Ahmadinejad has remained defiant, saying Tehran will never give up its right to nuclear power.
It has vowed repeatedly to install thousands of the centrifuges that, when run in a series, enrich uranium.
Mr Heinonen said the two parties had reached agreement on how to proceed with the negotiations over Tehran's nuclear programme, without giving further details.
Earlier this week, the head of the International Atomic Energy Agency, Mohammed ElBaradei, said that if Tehran answered the outstanding questions the agency had, the UN Security Council might not go ahead with a threat to impose a third set of sanctions on Iran.
He also said Iran had slowed down its controversial uranium enrichment process, and that he hoped that slowdown would lead to a complete suspension of enrichment, as demanded by the Security Council.