The meeting in Vienna of nuclear and other experts from Iran and the United States, France, Germany, Russia, China and Britain was to prepare for a new round of higher-level negotiations next week, also in the Austrian capital.
A spokesman for European Union foreign policy chief Catherine Ashton – whose office is coordinating contacts with Iran on behalf of the big powers – confirmed that the meeting had started but gave no details. Officials earlier said they were expected to last until Saturday.
The April 8-9 meeting of chief negotiators – including Ashton and Iranian Foreign Minister Mohammad Javad Zarif – will be the third round of talks at that level since February.
The aim is to hammer out a long-term deal by July 20 that would define the permissible scope of Iran’s nuclear programme in return for a lifting of sanctions that are severely battering its oil-dependent economy.
Both sides have made clear their political commitment to reach a comprehensive agreement but officials acknowledge that success is far from guaranteed in view of decades of mutual mistrust and big differences over the issues involved.
The powers want Iran to significantly scale back its nuclear activities in order to deny it any capability of quickly diverting them to the production of a nuclear bomb, if it decided to “weaponise” its enrichment of uranium.