Iran's top negotiator, Saeed Jalili, who said before the talks that he intended to bring "new initiatives" to the table, was meeting with delegates from the United States, France, Russia, China, Britain and Germany, CNN reported.
U.S. and European officials suggested if Iran shows a serious commitment to negotiating, the talks could continue in late May, The New York Times reported.
"I hope what we will see today is the beginnings of a sustained process," said Catherine Ashton, the European Union foreign policy chief who is chairing the meeting. "What we are here to do is to find ways in which we can build confidence between us and ways in which we can demonstrate that Iran is moving away from a nuclear weapons program."
Ashton said "much depends on what Iran is putting on the table today."
Iran, which agreed to the talks after more than a year with no negotiations, has said its nuclear program is only for peaceful purposes but Western countries have expressed concern it is working to develop nuclear weapons.
Diplomats said Iran could help restore confidence by allowing inspectors from the International Atomic Energy Agency to visit all nuclear sites, including the ones Iran refused to show the inspectors in February.
The United States and European countries have imposed sanctions on Iran in an attempt to get the country to restrict its nuclear program.