U.S. Secretary of State John Kerry will join nuclear talks between major powers and Iran in Geneva on Friday in an attempt to nail down a long-elusive accord to start resolving a decade-old standoff over Tehran's atomic aims, Reuters reported.
Kerry, on a Middle East tour, will fly to the Swiss city at the invitation of European Union foreign policy chief Catherine Ashton in "an effort to help narrow differences" in the negotiations, a senior State Department official said.
Ashton is coordinating talks with Iran on behalf of the five permanent U.N. Security Council members plus Germany.
After the first day of meetings set for Thursday and Friday, both sides said progress had been made towards an initial agreement under which the Islamic state would curb some of its nuclear activities in exchange for limited relief from punitive measures that are severely damaging its oil-dependent economy.
U.S. President Barack Obama said the international community could slightly ease sanctions against Iran in the early stages of negotiating a comprehensive deal on Tehran's atomic program to remove fears about Iranian nuclear intentions.
"There is the possibility of a phased agreement in which the first phase would be us, you know, halting any advances on their nuclear program ... and putting in place a way where we can provide them some very modest relief, but keeping the sanctions architecture in place," he said in an interview with NBC News.
Negotiators in Geneva cautioned, however, that work remained to be done in the coming hours in very complex talks and that a successful outcome was not guaranteed. Iran rejects Western accusations that it is seeking a nuclear bomb capability.
In Geneva, Iranian Deputy Foreign Minister Abbas Araqchi said it was too early to say with certainty whether a deal would be possible this week, although he voiced cautious optimism.
"Too soon to say," Araqchi told reporters after the first day of talks between Iran and the United States, Russia, China, Britain, France and Germany. He added, "I'm a bit optimistic."
"We are still working. We are in a very sensitive phase. We are engaged in real negotiations."
The fact that an agreement may finally be within reach after a decade of frustrated efforts was a sign of a dramatic shift in Tehran's foreign policy.
The Islamic Republic, which holds some of the world's largest oil and gas reserves, wants them to lift increasingly tough restrictions that have slashed its daily crude sales revenue by 60 percent in the last two years.