The €340m project will be fully financed by the Italian government through the Unblock Italy programme and is now awaiting the green light from the Ministry of Infrastructure and Transport and the Italian Committee for Economic Planning (Cipe).
The 3.4km extension will include a 3.2km underground section and four new stations, three of them underground.
The terminus at Cascine Vica will be a park-and-ride station with spaces for up to 350 cars.
Construction will begin next year and the extension is due to be commissioned in 2020.
