* Caisse yet to secure agreements over government funding
* Total cost of project rises to C$5.9 billion
* Cost is C$400 million higher than previously thought (Adds comment from Caisse CEO)
By Matt Scuffham
TORONTO, Nov 25 (Reuters) - Quebec's public pension fund said on Friday that its plan to build the world's third-largest light rail system in Montreal would cost C$400 million ($296 million) more than expected and it had yet to secure the required funding from the federal government.
The Caisse de depot et placement du Quebec, Canada's second- biggest public pension fund, said on Friday that the cost of building the railroad had risen to C$5.9 billion ($4.37 billion) to cover three additional stations.
It is planning to build a 67 km (42 miles) rail network that will link downtown Montreal with several suburbs and the city's airport.
The Caisse said it would increase its investment by C$100 million to C$3.1 billion, while Montreal's mayor said the city will invest C$100 million. Talks with the federal and provincial governments over the remaining funding are continuing.
Quebec's transport minister confirmed on Friday the province planned to provide a yet-to-be-decided level of investment in the project and said talks with the federal government over the remaining investment were "going well."
The fund plans to provide more than half the money with the rest coming from provincial and federal governments.
"There's a very important appetite to participate in the financing of this project. That being said, there's still work to be done with the governments of Quebec and Canada to finalize the details," said Caisse Chief Executive Michael Sabia.
Canada is planning to boost spending on infrastructure projects by an extra C$81 billion in the next 12 years in a bid to revitalize its economy and the Caisse project could be one of the first to include investment from a new infrastructure bank being set up by the country's Liberal government.
However, the project is different from many partnerships between public and private investors because the Caisse is taking on all of the construction and operational risk and will own and operate the rail system once it is built.
The Caisse aims to get the first trains up and running by 2020 and, to do that, Sabia said the Caisse must secure government funding in the next 4 1/2 months in order to start the work next spring.
"We will need a final decision around the first or second quarter so, calm down, it's not a crisis we're talking about here," Sabia told reporters.
$1 = 1.35 Canadian dollars Reporting by Matt Scuffham; Editing by Dan Grebler and Bill Trott