Deschamps, a former France skipper who led the team to 1998 World Cup glory, has been at the coaching helm of Les Bleus since summer 2012.
The decision to extend his contract will be made official by the French football federation at a press conference later Tuesday, the source told AFP.
Federation president Noel Le Graet had previously said that a contract extension for the 51-year-old Deschamps was dependent on France qualifying for the 2020 European championships.
Deschamps duly guided France into the competition, where they have been drawn alongside 2014 world champions Germany, reigning European champions Portugal and one more team still to qualify through the play-offs.
Deschamps will shortly become the longest-serving France coach, overtaking the eight years and six months of service by Michel Hidalgo between January 1976-June 1984.