The fourth round of nuclear talks between Iran and the 5+1 began in Vienna after EU foreign policy chief Catherine Ashton and the Iranian foreign minister met for a working dinner last night, Tuesday May 13, to set the framework for the talks.

ISNA reports that Mohammad Javad Zarif assessed the meeting with Ashton as “positive and constructive.”

The two sides are now looking at the hard task of drafting a final nuclear agreement, and Zarif has predicted that “unanticipated differences” may arise at this stage. Therefore, he has predicted there will be several meetings in the coming months.

According to the Geneva interim deal reached by the parties last November, a final deal needs to be reached within six month of its implementation in January 2014.