President Jacob Zuma of South Africa is expected in Tripoli for talks with Libyan leader Muammar Gaddafi.
It is unclear if the visit, Mr Zuma's second to Libya, will focus on exit strategies for Colonel Gaddafi.
Spokesman Zizi Kodwa said Mr Zuma's visit on Monday was part of efforts by the African Union to persuade Libya to adopt political reforms needed to end the crisis.
The BBC reports that the rebels refuse to negotiate unless Colonel Gaddafi steps down. They have been fighting government forces since February.
Meanwhile, the African National Congress has condemned the NATO bombing of Libya.
NATO imposed a no-fly zone in Libya in March.