Iran appears ready to scale back activity of potential use in making nuclear bombs, suggesting it is willing to compromise for a deal to win relief from harsh economic sanctions, diplomats said this evening.
Follow-up talks will be held on 7 and 8 November.
Details of Iran's proposals, presented during two days of nuclear negotiations in Geneva with six world powers, have not been released.
Western officials are not unsure whether Iran is prepared to go far enough to clinch a breakthrough deal.
But, in a clear sign of hope, European Union foreign policy chief Catherine Ashton said it was agreed to hold the next round of negotiations in three weeks in Geneva.
Iran's chief negotiator praised this week's discussions as "fruitful".
After a six-month hiatus, Iran and the United States, Russia, China, France, Britain and Germany began negotiations in earnest yesterday to end a long stand-off.
Diplomatic paralysis reigned during the eight-year tenure of previous Iranian president Mahmoud Ahmadinejad.
But a door to serious negotiations opened in June with the landslide election of moderate Hassan Rouhani on a platform of conciliation to overcome Iran's international isolation.
The powers want the Islamic Republic to stop higher-grade uranium enrichment to allay concerns that it would provide Iran a quick path to bomb-grade nuclear fuel.
Iran says it is refining uranium only to generate more electricity for a rapidly expanding population and to produce isotopes for medicine.
Ms Ashton told a closing news conference that the powers were "carefully" examining Iran's proposals and that this week's discussions were "the most detailed we have ever had, by, I would say, a long way".
Ms Ashton, presiding over the talks on behalf of the six powers, said the two sides had agreed that nuclear and sanctions experts would convene before the next high-level negotiations.
Iranian Foreign Minister and chief negotiator Mohammad Javad Zarif said Iran looked forward to a new era in diplomatic relations.
"We sense that members of the [six powers] also have exhibited the necessary political will in order to move the process forward. Now we need to get to the details," he told reporters.
He said the two sides had for the first time agreed on a joint statement after the talks, but declined to elaborate on what had been discussed.
After yesterday’s initial round, Iranian Deputy Foreign Minister Abbas Araqchi suggested Iran was prepared to address long-standing calls for the U.N. nuclear watchdog to have wider and more intrusive inspection powers.
He also told the official IRNA news agency that measures related to its uranium enrichment were part of the Iranian proposal, but hinted the Islamic Republic was not inclined to make its concessions quickly.