Iranian Foreign Minister Mohammad Javad Zarif and US Secretary of State John Kerry have arrived in the Austrian capital and are going to meet today to accelerate the process of drafting the text of a final nuclear deal, dubbed the Joint Comprehensive Plan of Action (JCPOA).

Foreign ministers of Britain, France and Germany as well as the European Union's foreign policy chief Federica Mogherini will also join the high-profile talks on Sunday.

The EU coordinates diplomacy with Iran on behalf of the six powers.

Russian Foreign Minister Sergei Lavrov and China’s Wang Yi are also expected to join their counterparts later.

Top Iranian negotiators and deputies to foreign minister, Abbas Araqchi and Majid Takht Ravanchi, have been holding regular daily meetings with EU deputy foreign policy chief, Helga Schmid, in Vienna since June 17 in a push to finalize the text of the accord.

Experts from the two sides have been also holding tight meetings concurrent with the deputy-level talks.

On Friday, Araqchi said “major problems” have obstructed the process of drafting the final parts of the agreement.

“Overall, the work is being done with difficulty and slowly,” he noted.

Iran and the Group 5+1 (alternatively known as the P5+1 or E3+3) have been negotiating over the past 22 months to hammer out a lasting accord that would end more than a decade of impasse over Tehran's civilian nuclear program.

On April 2, the two sides reached a framework nuclear agreement in Lausanne, Switzerland, with both sides committed to push for a final deal until the end of June.

Tasnim News Agency's Abbas Aslani reporting from Hotel Coburg