A top US official says the negotiations underway in the Swiss town of Lausanne between Iran and the P5+1 over Tehran's nuclear energy program may go into Wednesday, Press TV reported.
The senior State Department official told AFP on Tuesday that diplomats and experts were "working around the clock" to narrow the differences over the Iranian nuclear issue in order to meet a self-imposed March 31 deadline for reaching a mutual understanding over the sticking points.
"Our team is evaluating where we are throughout the day and making decisions about the best path forward," the official said, speaking on condition of anonymity.
"We will of course keep working if we are continuing to make progress, including into tomorrow, if it's useful to do so. At this time, no decisions have been made about our travel schedule," the official noted.
Top officials from Iran and the P5+1 - the US, Britain, France, China, Russia and Germany - are engaged in intense negotiations to reach a comprehensive deal on the Islamic Republic's civilian nuclear program. The two sides have set July 1 as the deadline for a final agreement.
On Tuesday, Iranian Foreign Minister Mohammad Javad Zarif held meetings again with US Secretary of State John Kerry and his other counterparts from the P5+1 in Lausanne.
High Representative of the European Union for Foreign Affairs and Security Policy Federica Mogherini also participated in the discussions.
Meanwhile, Russian Deputy Foreign Minister Sergei Ryabkov, Iranian deputy foreign ministers, Abbas Araqchi and Majid Takht-e Ravanchi, US Under Secretary of State for Political Affairs Wendy Sherman as well as Mogherini's deputy, Helga Schmid, also attended the negotiations.
Kerry told a CNN correspondent in Lausanne on Monday that he and his global counterparts were working hard to resolve "tricky issues" obstructing a nuclear agreement with Iran.
"There still remain some difficult issues. We are working very hard to work those through," Kerry said.