Iran's Zarif 'sees signs of comprehensive nuclear deal'
Iran's foreign minister has said he sees "signs" of a comprehensive deal on its nuclear programme, after talks with world powers, Iranian media report.
Mohammad Javad Zarif was quoted by the Fars news agency as saying "an understanding is possible that respects the rights of the Iranian nation".
Earlier, he and EU foreign policy chief Catherine Ashton said their two days of talks in Vienna had been "substantive".
They also agreed to resume discussions in the Austrian capital next month.
Iran and the P5+1 - the US, UK, France, China and Russia plus Germany - are seeking to build on an interim deal signed in November, which saw Tehran curb uranium enrichment in return for partial sanctions relief.
The world powers want Iran to scale back its sensitive nuclear activities permanently to ensure that it cannot assemble a nuclear weapon.
But Iran says its nuclear work, which it insists is peaceful, will continue - and wants an end to the sanctions that have crippled its economy.
After their latest meeting, Mr Zarif and Baroness Ashton issued a joint statement saying they had "substantive and useful discussions covering a set of issues", including uranium enrichment, the heavy-water reactor at Arak, civil nuclear co-operation and sanctions.
"We will meet again on 7-9 April 2014 in Vienna and continue our work on the substantial areas which we intend to cover in a comprehensive agreement. In the meantime, technical experts will meet to further elaborate on the details of the relevant issues."
Mr Zarif subsequently told reporters: "At this stage we are trying to get an idea... of the issues that are involved and how each side sees various aspects of this problem."
He added that he was "optimistic" about meeting the 20 July deadline for a long-term deal.
However, a senior US official warned that it would be very difficult to overcome the issues surrounding Iran's uranium enrichment activities, including monitoring, the Natanz and Fordo facilities, and its stockpiles of enriched uranium.
"It's a gap that's going to take some hard work to get to a place where we can find agreement," the official said.
The official added that differences over the heavy-water reactor under construction at Arak, from whose spent fuel plutonium could be extracted by a reprocessing plant, remained similarly wide.
Without giving details, the official said there were "many options" for Arak.
The US has previously suggested converting it into a light-water reactor, which experts say would produce less plutonium and therefore present less of a proliferation threat.
Mr Zarif told reporters on Wednesday that the Arak reactor was "part of Iran's nuclear programme and will not be closed down" but did not explicitly rule out modifying it.
Last month, the head of the Atomic Energy Organisation of Iran said it could introduce some design changes to allay the P5+1's concerns.