(CNN)Secretary of State John Kerry met with Iranian Foreign Minister Mohammad Javad Zarif Saturday morning in Vienna as the representatives for the two countries worked toward finalizing a nuclear deal.
Kerry meets with Zarif ahead of Iran nuclear deal deadline
The two met for about an hour and a half, took a roughly 90-minute break and then resumed discussions.
Asked if he was optimistic about an agreement, Kerry said, "I think it's fair to say that we're hopeful."
"We have to work to do," he added. "There are some very tough issues and I think we all look forward to getting to the final effort here to see whether or not a deal is possible. I think everybody would like to see an agreement. But we have to work through some difficult issues."
Zarif said that while there remained differences on the "issues" being discussed, both he and Kerry agree that more work is needed.
"We're determined to do everything that we can in order to be able to make this important milestone. But that depends on a lot of things and were determined to work on them and find out," Zarif said.
Energy Secretary Ernest Moniz and Wendy Sherman, under secretary of state for political affairs, were also in the meeting.
Saturday night, Kerry met for about an hour with French Foreign Minister Laurent Fabius, a senior State Department official told CNN. The secretary offered his condolences on the terrorist attack that occurred Friday, and they discussed the attacks in Tunisia and Kuwait as well. But the bulk of their meeting was spent discussing the Iran deal.
Kerry is set to meet with Zarif again Sunday morning, and will also meet with European Union High Representative Federica Mogherini as well, the official added.
Iran and the U.N. Security Council's permanent members hope to negotiate a comprehensive nuclear deal before June 30. Until now, it has been difficult to get the Iranians to focus on the details of an agreement.
U.S. officials do not expect to have an agreement by the deadline. Sources say they hope a deal is finalized by July 3, but understand that things could last much longer.
One of the most sensitive issues needing to be addressed is granting International Atomic Energy Agency inspectors access to Iranian nuclear sites, including military ones. There seems to be less focus on making Iran confess about its past developments of a nuclear weapon than it is about current affairs and future compliance.
The second outstanding issue is related to sanctions being lifted or suspended against Iran.