US Secretary of State John Kerry is consulting with allies on how to reach a nuclear deal with Iran.

The State Department said Kerry met German foreign minister Frank-Walter Steinmeier in Vienna on Saturday.

The US and Iran remain divided on how much Tehran needs to constrain programmes that could make nuclear weapons. Iran has said all its programmes are meant for peaceful uses, but is negotiating because a deal would result in sanctions relief. The differences are expected to result in the talks being extended beyond tomorrow's target date for a deal.