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Iran nuclear talks: World powers seek deal in Lausanne
Representatives of six world powers are intensifying talks with Iran on its nuclear programme, ahead of a 31 March deadline for a deal.
The US secretary of state and German and French foreign ministers have all cancelled their travel plans in a final push for an agreement.
Representatives from China, Russia and the UK are also at the negotiations.
US officials say all parties have agreed to a "step by step approach" to the deal, but sticking points remain.
The world powers, known as the P5+1 group - the five permanent members of the UN Security Council plus Germany - want to ensure that Iran cannot develop nuclear weapons.
Iran denies it is aiming to build nuclear weapons and is hoping that a deal will lead to the lifting of international sanctions.
