File Photo: US Secretary of State John Kerry, right, speaks with Iranian Foreign Minister Mohammad Javad Zarif, as they walk in Geneva, Switzerland, ahead of the next round of nuclear discussions Wednesday, Jan. 14, 2015 (Photo: AP)
A senior Iranian official in talks on the country's disputed nuclear programme has said differences remain on key questions at the ongoing negotiations in Geneva, state media reported Monday.
"The gap still exists, differences exist, and all parties are negotiating with seriousness and determination, but we haven't found solutions to key questions," Deputy Foreign Minister Abbas Araghchi said.
He was speaking after three hours of talks on Sunday night between US Secretary of State John Kerry and Energy Secretary Ernest Moniz and their Iranian counterparts Mohammad Javad Zarif and Ali Akbar Salehi.
The US and Iranian officials began their talks on Friday.
Parallel negotiations were held on Sunday between Tehran and senior negotiators from the so-called P5+1 group -- UN Security Council permanent members Britain, China, France, Russia and the United States plus Germany.
"In many areas, the negotiations have addressed the details... In some cases, solutions were found and the time has come for political decisions," said Araghchi, quoted by state television.
"For this reason, contacts at the highest level between the two parties are needed," he added.
Iran and world powers are trying to strike a deal that would prevent Tehran from potentially developing a nuclear bomb in return for an easing of punishing international economic sanctions.
Kerry and Zarif are holding a second day of discussions on Monday as the clock ticks down to a March 31 target for a framework accord.