Iran and major powers will meet again next month to try to narrow differences over Tehran's nuclear program after making limited progress on Sunday, Reuters reported.
All sides agreed to step up efforts to reach a political understanding by the end of March with a view to clinching a full-blown deal by their self-imposed deadline of June 30.
"The mood was very good, but I don't think we made a lot of progress," France's negotiator Nicolas de la Riviere told reporters as he left the European Union mission in Geneva.
Iranian deputy foreign minister Abbas Araqchi said that discussions had been "good" and "extensive".
"We reviewed all subjects on the table and we had very serious and business-like negotiations," he told reporters.
"We are still trying to bridge the gap between the two sides."
China's envoy to the talks confirmed that the next round of negotiations is set for early February, but said the venue has not been decided.
The weekend negotiations, held at the level of political directors, capped five days of diplomacy in Geneva and Paris, including lengthy meetings between U.S. Secretary of State John Kerry and Iranian Foreign Minister Mohammad Javad Zarif.
"Substantive progress is limited, experts will continue tomorrow (Monday) morning. It is fair to say that everybody is committed to stepping up efforts," a diplomat told Reuters.
EU political director Helga Schmid chaired the talks among officials from Iran, Britain, China, France, Germany, Russia and the United States. Acting Deputy Secretary of State Wendy Sherman declined comment.
Following an interim accord in November 2013, two deadlines for a final deal have been missed, and now a third one is looming on July 1. Before the talks were extended until July, Iran was toughening its stance, with Araqchi saying he sees no prospect for a deal unless the other side abandons its “illogical excessive demands”.
A senior Iranian official followed those comments by declaring that Iran will demand that all Western sanctions be lifted as part of a final deal, rejecting an American proposal of a gradual lifting of sanctions.
On Saturday, Zarif said that the only way to reach an agreement is if the West “stops pressuring” his country.
"If the Western countries want to negotiate with the Islamic Republic of Iran, they must make a political decision, which for some could be difficult, and stop with the pressure," he said.