The top Iranian and US diplomats met for an hour and a half on Sunday morning before a short break. Zarif and Kerry went face to face again early afternoon with just two days left before the July 7 deadline for a comprehensive nuclear deal.
Head of the Atomic Energy Organization of Iran (AEOI) Ali Akbar Salehi and US Energy Secretary Ernest Moniz also met on Sunday.
The Iranian deputy foreign ministers, Abbas Araqchi and Majid Takht-e Ravanchi, held talks with European Union deputy foreign policy chief, Helga Schmid, until late on Saturday working to settle differences on the text of a final deal and its annexes.
Iran and the five permanent members of the UN Security Council - the United States, Britain, France, Russia and China - plus Germany have been holding intense talks in the Austrian capital over the past nine days to nail down a final nuclear deal by Tuesday.
Meanwhile, the foreign ministers of France, Germany and Britain are expected to return to Vienna Sunday evening. Their Russian and Chinese counterparts will possibly join the talks on Monday.
A major issue hindering a final accord seems to be about the way sanctions against Iran should be lifted. Iran insists that all economic and financial restrictions should be removed completely on the very day a deal is signed.
In a live program from Vienna broadcast by IRIB on Saturday, Araqchi said all economic and financial sanctions against Tehran will be lifted on the day of finalizing a deal.
“On the day of the agreement, all economic and financial sanctions by the EU, the US, and the UN Security Council will be removed and we will take measures to meet [our] obligations,” the top Iranian negotiator said.