U.S. Secretary of State John Kerry and E.U. foreign policy chief Catherine Ashton are preparing for another day of nuclear negotiations with Iran.

They hope to narrow gaps in search of a deal that would offer Iran sanctions relief in exchange for proving its atomic ambitions are peaceful.

A senior U.S. official says Kerry and Aston are to meet separately at the luxury Geneva hotel where they are both staying on Saturday morning before inviting Iranian Foreign Minister Javad Zarif to join them. There was no immediate indication of how long the three-way meeting would last. On Friday, the trio met for five hours.

The negotiations appear to have made some progress in a major diplomatic push despite fierce opposition from Israel and uncertainty in Congress.