US State Secretary John Kerry will remain in Vienna to hold talks with the P5+1 group, EU High Representative Federica Mogherini and Iranian Foreign Minister Mohammad Javad Zarif on Tehran's nuclear program, US State Department spokeswoman Marie Harf said on Tuesday.

VIENNA (Sputnik) — According to the spokeswoman, the sides reached substantial progress in every area.

"We are taking these negotiations day to day to see if we can conclude a comprehensive agreement. Secretary Kerry will remain in Vienna to continue discussions with our P5+1 partners, High Representative Mogherini, and Foreign Minister Zarif," Harf said in a statement.

By Sputnik News