Recent heavy fighting in the Libyan capital of Tripoli mean elections are unlikely to take place as planned on December 10, the United Nations envoy said on Sunday.
Rival factions agreed to hold a national election before the end of the year, at a meeting in Paris in May.
"There is still a lot to do. It may not be possible to respect the date of December 10," UN Special Envoy to Libya, Ghassan Salame, told AFP.
"We can hold elections in the near future, yes. But certainly not now," he said, from the UN compound.
He said it might be possible in “three or four” months’ time.
Militia clashes in Tripoli's suburbs have left more than 100 people dead since late August.
Libya remains divided between the UN-backed Government of National Accord (GNA) based in Tripoli and a rival administration in the east that has support from Egypt, Russia and the UAE.
The GNA was set up under a 2015 UN-brokered deal that raised hopes of easing the chaos that followed the 2011 Nato-backed revolution which ousted Libyan dictator Muammar Qaddafi.
The Paris meeting brought together for the first time GNA head Fayez Al Sarraj and the powerful military styled leader Khalifa Haftar, whose Libyan National Army dominates the country's east.
Also present were Aguila Saleh Issa, the parliamentary speaker based in the eastern city of Tobruk, and Khalid Al Mishri, the head of the High Council of State.
The Paris agreement included a September 16 deadline to come up with an electoral law, forming the "constitutional base" for a vote later in the year.
But many observers have said the timetable was overly ambitious given ongoing instability and territorial disputes across the country, along with an economy that is flagging, despite Libya's vast oil wealth.
The United Nations is hoping that presidential and parliamentary elections will help to turn the page on years of chaos in Libya.
On Monday, France called for stronger UN sanctions on Libyans who stand in the way of a political solution.