Turkey has already sent military supplies to the GNA despite a United Nations arms embargo, according to a U.N. report seen by Reuters last month. Haftar, meanwhile, has received support from Russia, Egypt and the United Arab Emirates.
Turkey and Russia have been cooperating in the search for a political solution to Syria's eight-year war, even though they back opposing sides. They also have strong ties in defence and trade.
Erdogan's visit to Tunis comes as Turkey ramps up efforts to strike deals with nations around the Mediterranean, where Ankara has been at loggerheads with Greece over resources off the coast of the divided island of Cyprus.