Following months of negotiations, the federal government will announce $1.3 billion in funding for Montreal's light-rail project on Thursday, Radio-Canada has learned.

Prime Minister Justin Trudeau, Quebec Premier Philippe Couillard, Montreal Mayor Denis Coderre and the head of the Caisse de dépôt et placement du Québec, Michael Sabia, are expected to make the announcement in Montreal.

The decision comes a few months after the Trudeau government made no mention of funding the project in their spring budget, prompting concern from Couillard.

The price tag for the 67-kilometre rail line (LRT), which would link downtown with the South Shore and the West Island, has risen to $6 billion in order to add more stations in the city's downtown area.

Quebec has already committed around $1.3 billion to the project. The province's pension fund manager, the Caisse, has pledged close to $3 billion.

The LRT project now includes 27 stations. The first trains are expected to run in 2020.