Iran and six world powers returned to the negotiating table today with only two months left to overcome key differences hindering a deal on curbing Tehran's nuclear program.
No major breakthroughs are expected at the talks that are to continue until the end of next week, but the pressure is on both sides to find ways to narrow the gaps.
EU foreign policy chief Catherine Ashton sat down with Iranian Foreign Minister Mohammad Javad Zarif at UN headquarters to kick off the talks, alongside negotiators from six powers of the so-called P5+1.
It was the first meeting between Iran and P5+1 - Britain, China, France, Russia, the United States plus Germany - since July when they decided to extend the deadline for a deal to November 24.
But on the eve of the talks, a senior US administration official downplayed expectations of major progress, saying, "It's tough, very tough."
"Coming into New York, I think many of us were not optimistic," said the official, who asked not to be named.
"But it is clear that everyone has come here to go to work."
Iran has long denied it is seeking to develop a nuclear bomb, but the West is demanding Tehran agree to monitoring and safeguards while scaling back production of material that could be used for military purposes.
Negotiators say there are major hurdles to overcome but that holding talks in New York on the sidelines of the UN General Assembly will allow for some high-powered diplomacy to come into play.
A ministerial-level meeting of the P5+1 with Iran is expected next week and US Secretary of State John Kerry is scheduled to hold bilateral talks with Zarif.
US President Barack Obama last year held a historic phone call with Iranian President Hassan Rouhani, the first direct talks since the 1979 Islamic Revolution, but no contact is planned this time around.
Both leaders face strong domestic pressure to take a hard line on the nuclear issue, which has been a diplomatic headache for more than a decade until a deal was reached last year to try to break the logjam.
"This is an opportunity, because everybody's here," said the US official. "So we ought to make use of that to try to deal with all of these tough issues."
The meeting at UN headquarters is held against the backdrop of a US-led campaign to confront Islamist fighters in Iraq and Syria, where Iran wields influence as a key regional power.
Western nations agreed to lift some sanctions against Iran last year in exchange for agreement from Tehran to curb some nuclear activities and to get to work on a comprehensive agreement.
