Three days ahead of deadline, U.S. Secretary of State John Kerry is consulting with allies on how to overcome deep obstacles to reach a nuclear deal with Iran.

The State Department says Kerry will meet German Foreign Minister Frank-Walter Steinmeier when Steinmeier arrives in Vienna later Saturday. He also plans to talk to French Foreign Minister Laurent Fabius, who already is in the Austrian capital, as well as others by telephone.

The U.S. and Iran remain divided on how much Tehran needs to constrain programs that could make nuclear weapons. Iran says all its programs 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 the Monday target date for a deal.