Jeffrey Feltman, the UN under-secretary of state for political affairs, will also travel to neighboring Tunisia during his visit until Friday, said a UN statement.
The United Nations has launched a plan to bring stability to Libya through elections and changes to a 2015 political deal that set up a government of national accord led by Prime Minister Fayez al-Sarraj.
After two meetings were held in Tunis last year, there appears to have been little progress.
There is a "window of opportunity" to focus efforts on building unified state institutions, he added.
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There was no immediate information on Feltman's meetings.
Despite the 2015 accord, Libya remains divided between the UN-backed government in Tripoli and a rival administration in the east that enjoys support from Egypt, Russia and the United Arab Emirates.
One of the main stumbling blocks is the inclusion in the new government of Khalifa Haftar, the powerful leader whose Libyan National Army dominates the country's east.