Iranian chief nuclear negotiator, Saeed Jalili, left Tehran for Geneva on Wednesday ahead of talks on Iran's nuclear program. He is set to meet the top diplomats from the five permanent UN Security Council members and Germany on Thursday.
The talks are the first on Tehran's disputed atomic program in more than a year.
The six powers want Iran to respond substantively to their offer of trade and political incentives, in exchange for a suspension of sensitive nuclear activities and improved cooperation with UN inspectors.
But Western diplomats said Jalili was unlikely to have a response.