“As they examine your recommendation for an amended mandate for the United Nations Support Mission in Libya (UNSMIL), the members of the Security Council request that you establish and deploy swiftly an advance team to Libya,” the council said in a letter to Guterres that was seen by AFP.
Libya has been torn by civil war since a NATO-backed uprising led to the ouster and killing of long-time dictator Muammar Al-Qaddafi in 2011.
Control of the country is now split between the Tripoli-based Government of National Accord (GNA) and its rival, the eastern-based House of Representatives backed by military strongman Khalifa Haftar, who launched a failed offensive to seize the capital in 2019.
A fragile ceasefire agreed in Geneva in October has largely held, despite threats by Haftar to resume fighting.
In the letter, the council said it expected within 45 days to receive reporting on preparations undertaken by the advance team and practical proposals for amending the mandate of the UN mission in Libya.
In a report late last year, Guterres called for the creation of an unarmed observer group for Libya, made up of civilians and retired military people from countries of the African Union, the European Union and the Arab League. He did not say how big it should be.
Deployment of ceasefire observers is being carried out with the approval of the parties in Libya.
The advance team of the observer force is expected to comprise around 30 people, diplomats said.