U.S. Secretary of State John Kerry and Iranian Foreign Minister Mohammad Javad Zarif resumed talks on Tuesday (March 3) on Iran's disputed nuclear program.
Kerry was seen walking along the lake with Under-secretary of State for Political Affairs Wendy Sherman as the two were going to meet Zarif at his hotel.
Kerry and Zarif already met on Monday for a few hours.
Both sides have postured and suggested that the other would be to blame if the talks fail to meet an end-March deadline for a framework agreement, with Kerry saying Iran must be prepared to compromise and Zarif calling for the total lifting of sanctions imposed on the Islamic Republic as part of any final deal.
One of the disputes holding up a final agreement is over the pace at which sanctions should be dismantled.
Tehran wants them rapidly removed while Western powers want gradual steps responding to Iranian performance in implementing the accord.
The West fears Iran wants to develop an atomic bomb. Tehran says its nuclear program is entirely peaceful.
Earlier, Iran rejected as "unacceptable" a demand by U.S. President Barack Obama that Tehran freeze its sensitive nuclear activities for at least 10 years, the semi-official Fars news agency reported. "Obama's stance ... is expressed in unacceptable and threatening phrases ... Iran will not accept excessive and illogical demands ... Tehran will continue nuclear negotiations with the six powers," Foreign Minister Mohammad Javad Zarif was quoted as saying by Fars. In an interview with Reuters on Monday, Obama said Iran must commit to a verifiable halt of at least 10 years on sensitive nuclear work for a landmark atomic deal to be reached between Tehran and six major powers.