US and Iranian officials were meeting for a second day of negotiations in Switzerland Friday as they work towards hammering out a full nuclear deal ahead of a November deadline.
The US team led by Deputy Secretary of State Bill Burns and Under Secretary Wendy Sherman began meeting Thursday with an Iranian delegation led by Iran's Deputy Foreign Minister Abbas Araqchi in a luxury Geneva hotel.
No information filtered out from the first day of closed-door talks, and it remained unclear whether they would wrap up Friday or continue into Saturday.
EU and US officials did announce Thursday that broader talks would be held on September 18 in New York between Iran and the United States, China, Russia, Britain, France and Germany, and would be led by European Union foreign policy chief Catherine Ashton.
That will mark the first meeting of the so-called P5+1 and Iran since they failed to meet a July 20 deadline for implementing a comprehensive and complex deal on curbing Tehran's enrichment capabilities and number of centrifuges.
The deadline has been pushed forward to November 24.
The West suspects Iran wants to acquire nuclear weapons, but Tehran insists the program is purely for peaceful purposes.
In exchange for accepting curbs on its nuclear activities, Iran wants a slew of crippling US, EU and UN sanctions to be lifted.
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But any deal will have to be approved by the Islamic leadership in Tehran as well as by the US Congress, where many lawmakers are seeking to impose even tougher sanctions on Iran.
The Geneva talks come after Washington last weekend unleashed a new round of sanctions against Tehran.
State Department deputy spokeswoman Marie Harf meanwhile called Thursday on Iran to "fully and without delay" cooperate with UN watchdog the International Atomic Energy Agency (IAEA), after its inspectors were refused access to a military base outside Tehran that they have been trying to visit since 2005.
Over the past year, Tehran and Washington have pursued exhaustive talks on the nuclear deal, marking a dramatic turnaround in relations for two countries that had virtually no official communication since the aftermath of the 1979 Islamic revolution, which toppled the Western-oriented shah.
Switzerland, which represents US interests in Tehran and has hosted many of the nuclear talks, only applies "targeted" economic sanctions on Iran that do not include oil.
The Swiss city of Lausanne has since 2003 hosted Iranian Oil Company subsidiary the Naftiran Intertrade Company Sarl (NICO), which for the past two years has been the target of EU sanctions.
Former NICO chief Seyfollah Jashnsaz in early July hailed "Switzerland's fairer approach to Iran", pointing out that the subsidiary had ensured $100 billion worth in Iranian oil sales between 2010 and 2014.
"We apply targeted sanctions. We do not want the sanctions to hurt everyone, especially in the civil society," Swiss Economic Affairs Ministry spokeswoman Livia Leu told public broadcaster RTS.