The United States on Thursday held the highest-level direct meeting with Iran in 30 years on the margins of six-party talks outside Geneva.
A diplomat who was at the meeting but spoke on condition of anonymity said William Burns, the US under secretary of state, had a "significant conversation" with Iran's chief nuclear negotiator, Saeed Jalili.
European Union foreign policy chief Javier Solana said Iran planned to cooperate fully with the International Atomic Energy Agency (IAEA) on inspections of a new enrichment facility concealed underground near the holy city of Qom.
Both the US and Iran described the talks between Tehran and the six powers as productive and agreed the contacts would be resumed by the end of the month.
Burns had sat in on a multi-party meeting with Iranian officials in July, but Thursday's encounter was the first time high-level senior officials had met face to face since the US severed diplomatic ties with the Islamic state following the 1979 revolution. Switzerland has represented US interests in Tehran since then.
Western officials are hoping the six-party talks, which also include Russia, Britain, France, Germany and China, will pressure Iran into "coming clean" on the nature of its nuclear programme, a US official told reporters in Washington this week.
"From this meeting we'll learn whether Iran is prepared to engage seriously, whether they're willing to enter into a process, whether they're willing to open up their programmes for meaningful international inspections," Philip Crowley, assistant secretary, said at a press conference two days before the meeting in Switzerland.
Iran is hoping the talks will put to rest fears that it plans to build a nuclear bomb. Iranian officials have said they would not give up their right to continue developing a nuclear programme.
swissinfo.ch and agencies