Last month Turkey offered Istanbul as the venue for talks expected to take place on April 13, a proposal which appeared to gather momentum last week when Iranian Foreign Minister Ali Akbar Salehi said Istanbul would be "the best option".
Turkey has repeatedly backed Iran's right to develop peaceful nuclear technology. The United States and its allies suspect Tehran of covertly working on nuclear weapons and have imposed tough new sanctions on its financial and energy sectors.
Tehran, which says its nuclear activities are purely peaceful, has agreed to renewed talks with the five permanent members of the Security Council - the United States, Russia, China, France and Britain - and Germany this month. Read More