The new round of talks between Iran and the world powers over Iran’s nuclear program has ended in Vienna, and the two sides are set to meet on May 13 to continue the negotiations.

Catherine Ashton, the EU foreign policy chief, said in a joint statement on Wednesday April 9 with Iranian Foreign Minister Mohammad Javad Zarif: “A lot of intensive work will be required to overcome the differences which naturally still exist at this stage in the process.”

The two sides are looking at drafting a final agreement in May.

Meanwhile, IAEA chief Yukiya Amano announced that Iran is responding well to inspectors from the UN watchdog and living up to its side of the bargain as stipulated in November’s Geneva agreement.

The talks also included negotiations between Iranian and U.S. representatives behind closed doors. Iranian deputy foreign minister Abbas Araghchi said since sanctions against Iran are largely unilateral sanctions by the U.S., they require “more serious and comprehensive talks.”