Top diplomats from six countries say they have narrowed differences with Tehran on curbing Iran's nuclear program, but could not say if they will reach an agreement.
U.S. Secretary of State John Kerry joined counterparts from Russia, Britain, France, China and Germany in Geneva Saturday in a continued effort to get Tehran to limit its uranium enrichment program. Kerry met separately with Russian Foreign Minister Sergei Lavrov on the sidelines of the meeting.
Swiss Foreign Minister Didier Burkhalter held talks with Iranian Foreign Minister Mohammad Javad Zarif on Saturday.
World powers say Iran's nuclear program can be used to develop nuclear arms and have imposed sanctions on the oil-rich country. Tehran argues that it is developing nuclear power for energy and other peaceful purposes.
Russian Deputy Foreign Minister Sergey Ryabkov told reporters Saturday that Iran's demand to continue construction of a reactor near its northern city of Arak remains one of the outstanding issues. He said it is not clear that narrowing the gap in Geneva talks will lead to a breakthrough.
British, German and French negotiators said there is still tough work ahead before a deal can be reached.
Experts say that when operational, the heavy-water reactor in Arak could yield bomb-grade plutonium.
Chinese diplomats say the talks that began Wednesday in Geneva have reached a final phase.
Meanwhile, Russian Deputy Prime Minister Dmitry Rogozin met with Iranian President Hassan Rouhani in Tehran on Saturday to discuss the issue.
European Union foreign policy chief Catherine Ashton has been leading the negotiations with the Iranians. The main sticking points have been to what extent Iran will be allowed to enrich uranium and how much sanctions against Tehran would be eased.