Two days before a deadline to reach an agreement on Iran’s nuclear program, U.S. officials said disagreements between the P5+1 group of world powers and Tehran remained. Talks are now expected to extend into July.

“Given the dates and that we have some work to do ... the parties are planning to remain in Vienna beyond June 30 to continue working,” a U.S. official told the Associated Press on the condition of anonymity. Iran is in negotiations over the country’s nuclear program with representatives of China, France, Germany, Russia, the U.K. and the U.S.

Iranian Foreign Minister Mohammed Javad Zarif was set to leave the Geneva talks Sunday and return to Tehran for discussions about the negotiations with Iran’s leaders. U.S. officials told Reuters Zarif’s travel plans were not unexpected. “Zarif will return to Tehran tonight and will come back to Vienna tomorrow,” according to an unnamed Iranian official quoted by the Tasnim News Agency in Iran.

Negotiations can technically be extended to July 9, the deadline for the U.S. Congress to receive the agreement. Congress then has 30 days to review the terms of the deal before President Barack Obama can suspend congressional sanctions. Any agreement reached after July 9 would give Congress a 90-day review period.

U.S. Secretary of State John Kerry was in Geneva for talks over the weekend, as were German Foreign Minister Frank-Walter Steinmeier and French Foreign Minister Laurent Fabius. China, Russia and the U.K. will soon send their representatives, AP reported. “I am convinced that if there is no agreement, everyone loses,” Steinmeier told German media. “Iran would remain isolated. A new arms race in a region that is already riven by conflict could be the dramatic consequence.”

However, Steinmeier’s British counterpart disagreed. “I have said many times before, and I’ll say again today: No deal is better than a bad deal,” Foreign Secretary Philip Hammond said while speaking to reporters Sunday. “There are red lines which we cannot cross and some very difficult decisions.”