"The primaries are a machine to produce unity … I want to be the candidate of reunion," Peillon said on France 2 television channel on Sunday.
Peillon noted that he decided to run for the presidency on the day when French President Francois Hollande said he would not seek re-election.
The ruling Socialist Party is preparing for two rounds of primaries in January. Former Prime Minister Manuel Valls is among the declared candidates for the Socialist Party's nomination.
The French presidential elections will take place in April and May 2017.