Iranian Foreign Minister Mohammad Javad Zarif said he saw "signs" Wednesday a long-term nuclear deal could be reached with major powers after the latest round of talks in Vienna.
"There are signs that an understanding is possible that respects the rights of the Iranian nation," the Fars news agency quoted Zarif as saying.
"It is planned that we start work during a meeting scheduled for the month of Ordibehesht (April 21 to May 21)... on drafting the text of an agreement," he said.
"That is to say we will have spent three months conducting comprehensive negotiations and will spend the next three months drawing up the final agreement."
Under an interim agreement Iran struck with the six powers in November, the two sides are aiming for a long-term deal by a July 20 target date.
The latest round of talks wrapped up on Wednesday, with EU foreign policy chief Catherine Ashton describing them as "substantive and useful."
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Zarif said he was "pleased" with the discussions so far on four key issues in any agreement -- Iran's Arak heavy water reactor, its enrichment of uranium, civil nuclear cooperation and the lifting of Western sanctions.
"On the (lifting) of the sanctions, it seems that we are getting close to an agreed plan," Zarif said.
But he said there was no agreement on the Arak reactor which Western governments want to remain uncompleted for fear that its plutonium waste could give Iran an alternative route to a nuclear bomb.
"The Arak rector is part of Iran's nuclear programme and will remain so. But if there are any concerns about the reactor, they should be addressed," he said.
Zarif said negotiations would continue at the experts level ahead of the next round of talks on April 7.
The six powers -- Britain, China, France, Russia and the United States plus Germany -- want Iran to reduce permanently, or at least for a long time, the scope of its nuclear activities in order to make it extremely difficult for it ever to develop nuclear weapons.
Iran has always denied any such ambition.