French President Emmanuel Macron will host the meeting, the presidency said in a statement today.
"France intends, through this initiative, to facilitate a political agreement" between the two rivals as the newly appointed UN envoy for Libya, Ghassam Salame, takes office, the statement said.
Tomorrow's talks, which were first reported by France's Journal du Dimanche newspaper yesterday, would be the second between Sarraj and Haftar in the space of three months after they met in Abu Dhabi in May.
Political rivalry and fighting between militias have hampered Libya's recovery from the chaos that followed the 2011 uprising that toppled and longtime dictator Moamer Kadhafi, who was killed in the aftermath.
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Sarraj's Government of National Accord has been struggling to assert its authority since it began work in Tripoli in March 2016. Haftar's rival administration based in the remote east has refused to recognise it.
Western intelligence services fear that Islamic State jihadists are capitalising on the chaos to set up bases in Libya as they are chased from their former strongholds in Iraq and Syria.
French Foreign Minister Jean-Yves Le Drian told newspaper Le Monde in June that Libya was "a priority" for Macron and said there was "a security risk because of the trafficking of all kinds, including humans" from Libya.
"In consultation with all its partners, France intends to show its support for the efforts to build a political compromise, under the aegis of the United Nations, which unites... All the different Libyan actors," Monday's statement from the Elysee Palace said.
"It is necessary for the control of Libyan territory and its borders, to fight terrorist groups and arms and migrant traffickers, but also with a view to a return to a stable institutional life.