NATO Secretary General Anders Fogh Rasmussen made an unannounced visit to Libya on Monday, a NATO spokesman said in Brussels.
Rasmussen will hold talks with National Transitional Council (NTC) head Mustafa Abdel Jalil and other Libyan leaders in Tripoli, the press service said. After the talks, Rasmussen and Abdel Jalil will hold a joint press conference.
NATO on Friday announced the end of Operation Unified Protector, which was imposed to protect civilians from Muammar Gaddafi's regime.
NATO is formally ending the mission on Monday, which it has hailed as one of its "most successful" yet.
The no-fly zone and naval blockade imposed by NATO on March 31 will end at 11:59 pm Libyan time (21:59 GMT), as stipulated by a UN Security Council resolution approved last week that ends the mandate for military action.
Over the seven months, NATO aircraft carried out more than 26,000 sorties, including 9,600 strike sorties. The alliance also maintained a naval blockade of Libya at the same time it facilitated delivery of 2,100 shipments of humanitarian aid.