GENEVA: UN-sponsored talks aimed at paving the way for elections in Libya in late December failed to find common ground, the deputy of the United Nations mission in Libya said on Friday night after weeklong talks near Geneva.

Raisedon Zenenga, assistant secretary-general and mission coordinator of the UN Support Mission in Libya (UNSMIL), called on participants to pursue the effort, describing the talks as "heated debate" marked by threats of walk outs.

"The people of Libya will certainly feel let down as they still aspire to the opportunity to exercise their democratic rights in presidential and parliamentary elections on 24 December," Zenenga told the closing session.

"This does not bode well for the credibility and future relevance of the LPDF (Libyan Political Dialogue Forum)," he said. "I encourage you to continue to consult among yourselves to pursue a workable compromise and cement what unites you." The talks, held at a hotel about 15 kilometres (9 miles) from Geneva, had been extended into a fifth day on Friday with delegates struggling to agree. They had been expected to establish the constitutional basis for presidential and parliamentary elections by July 1.

But delegates and UN officials said they could not agree among themselves on several proposals circulating, prompting organisers to extend the talks originally planned to last four days.

The elections would be a critical step in international efforts to bring stability to Libya, which has been in turmoil since a 2011 NATO-backed uprising against Muammar Gaddafi.

A UN-led peace process brought a ceasefire last summer after fighting between rival factions paused and then a unity government was formed.

The talks in Switzerland follow an international conference in Berlin last week.