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Keystone,Laurent Gillieron, Associated Press
British Foreign Secretary Philip Hammond, left, U.S. Secretary of State John Kerry, right, and U.S. Robert Malley, center, Senior Director for Iran, Iraq, and the Gulf States, National Security Council speak during a break outside the hotel at the Beau Rivage Palace Hotel as the Iran nuclear talks continue, in Lausanne, Switzerland, Wednesday, April 1, 2015.

LAUSANNE, Switzerland — German Foreign Minister Frank-Walter Steinmeier says negotiators at the Iran nuclear talks are still facing a "tough struggle," indicating the talks are not likely to end soon.

At the same time, he's holding out hope that the sides will be able to negotiate a preliminary accord that will let them embark on a new phase of talks aiming for a final deal by June.

For nearly a week, Iran and six powers have been locked in haggling over what that initial understanding should look like. The talks were extended past the Tuesday deadline in an effort to bridge differences.

Steinmeier said Wednesday that he hopes when the talks end "we won't just be reporting about closing gaps ... but also over agreement about important points."