US State Department spokeswoman Marie Harf has described as “constructive and useful” the nuclear negotiations between Iran and P5+1 in the Austrian capital, Vienna.

Negotiators discussed “both process and substance,” she said.

The talks, which commenced on February 18,  were presided over by Iranian Foreign Minister Mohammad Javad Zarif and EU foreign policy chief Catherine Ashton.

On February 19, Iranian Deputy Foreign Minister for Legal and International Affairs Abbas Araqchi said that Tehran and the six countries had finalized a framework for comprehensive talks to reach a final agreement.

The Iranian nuclear negotiator said that the talks were held in a positive atmosphere, IRNA reported.

The talks in Vienna mark the first round of high-level negotiations held between Tehran and the P5+1 after they clinched a landmark interim deal in the Swiss city of Geneva on November 24, 2013.

Under the deal, dubbed the Geneva Joint Plan of Action, the six countries undertook to provide Iran with some sanctions relief in exchange for Iran agreeing to limit certain aspects of its nuclear activities during a six-month period. It was also agreed that no nuclear-related sanctions will be imposed on Iran within the same timeframe. All sanctions must be lifted within a year.