World powers have ended two days of talks with Iran with no sign of a breakthrough.
The two sides have agreed to meet at expert level in Istanbul next month and to hold further high-level negotiations in Kazakhstan in April.
At the talks that ended in the Kazakh city of Almaty.
France, Germany, the US, China, Russia and Britain have offered to lift some sanctions if Iran scaled back nuclear activity the West fears could be used to build bombs.
Tehran denies seeking nuclear weapons.
Hopes of a significant easing of the deadlock in the decade-old dispute were dented when Russian media cited a source close to the talks as saying there had been no clear progress.
Iran said the expert-level talks between the two sides would be held in Istanbul on 18 March and another round of political negotiations in Almaty on 5-6 April.
Russia's negotiator, Deputy Foreign Minister Sergei Ryabkov, said the Istanbul meeting would take place on 17-18 March and gave the same dates as Iran of 5-6 April for the Almaty talks.
The meeting in Almaty that ended today was the first between the world powers and Iran in eight months.
Western officials described the first day of the talks as "useful". Iranian state television described the atmosphere in the discussions as "very serious".
The outcome will be closely watched in Israel, which has strongly hinted that it could attack Iran's nuclear sites if diplomacy and sanctions fail to stop Tehran's uranium enrichment programme.
Iran says Israel's assumed nuclear arsenal is the main threat to peace and denies Western allegations it is seeking to develop the capability to make atomic bombs.
It says it is only aiming to produce nuclear energy so that it can export more oil.
In their latest attempt to break years of stalemate in the dispute, the powers are offering Iran a relaxation of some of the sanctions that are taking a heavy toll on its economy.
Western officials have confirmed the offer includes some limited sanctions easing if Iran closes a underground site where it carries out its most controversial uranium enrichment work.
Diplomats had seen scant chances of a conclusive deal with Iran before a June presidential election - with the political elite preoccupied with domestic issues - but they had hoped to hold follow-up talks soon.