It is proposing a three stage project for the Saclay light rail route: Massy - Saclay to start, Saclay - Versailles and then Massy - Orly to finish, once the line 14 is extended to Orly. The light rail would work alongside line 14.
Pierre Mongin, president of the RATP, made the announcement at a press conference in Paris.
"If the League of Greater Paris retains the idea it could launch a tender which of course we will respond," he said.