Iran resumed technical talks with world powers in Geneva on Monday, a vital step in implementing a nuclear deal signed last month which suspends key elements of Tehran's nuclear programme in exchange for limited sanctions relief.
The talks between expert teams from Iran and six world powers are meant to translate the political deal into a detailed implementation plan by the end of January, Iran's state news agency, IRNA, quoted an unnamed source as saying.
A key sticking point appears to be how much advance information Western governments will get so they can verify that Iran is meeting its end of the deal before they lift any sanctions.
The third round of talks between technical experts from the permanent U.N. Security Council members - Britain, China, France, Russia and the United States - plus Germany, are set to last a day and resume in 2014, IRNA reported, a sign of the complexities facing the negotiators in reaching agreement on practical steps.
They began work on Dec. 9 but Iran broke off the talks in protest at the U.S. blacklisting an additional 19 Iranian companies and individuals under existing sanctions.
Iranian officials said the move violated the spirit of the deal but U.S. officials said it did not breach the agreement.
Iran rejects Western fears that its nuclear work has any military intentions and says it needs nuclear power for electricity generation and medical research.