The provincial transit agency Metrolinx has filed a notice of intent to cancel a nearly three-quarter-billion dollar contract for Bombardier to supply light-rail vehicles for LRT lines under construction in Toronto.

"There have been some concerns about Bombardier's performance as there have been significant quality and manufacturing issues that, to-date, have not been resolved," Metrolinx spokesperson Anne Marie Aikins told CBC News.

"As a result, we have taken the next step available to us through our contract."

The move comes just months after Metrolinx ordered 125 new bi-level commuter railcars from Bombardier in a contract valued at $428 million.

But the transit agency's confidence in the Canadian manufacturer has wavered before.

Bombardier calls move 'normal,' won't give reasons for delay

In July, Metrolinx expressed concern over delivery delays of a prototype test vehicle for the Eglinton-Crosstown and the Finch West light rail transit lines in Toronto. Bombardier was supposed to deliver that vehicle in 2014 but missed that deadline. The company missed another deadline for delivery of the vehicle earlier this week.

A letter from Metrolinx at the time also raised concerns about unresolved issues surrounding manufacturing and quality.

"We will continue to work with Bombardier on this issue and we will deliver on our transit commitments," Aikins said Wednesday.

On Thursday, Bombardier spokesperson Marc-Andre Lefebvre told CBC News the notice of intent is a "normal" part of the contractual process, but would not provide specifics on the reason for the delay.

"It's not something that surprises us," Lefebvre said of the notice, adding that Bombardier received a letter indicating Metrolinx's intent as early as last week.

'We need certainty,' transport minister says

Lefebvre denied delays in the roll-out of the light-rail vehicle prototype will impact production of the vehicles themselves, adding the prototype is only one of 182 light-rail vehicles, which aren't slated to begin rolling out until the second quarter of 2018 and aren't meant to be in service until 2021.

Asked what would become of the projects if Metrolinx does cancel the contract, Lefebvre said, "What we're focusing on is not the ifs but the now, and the progress that's being done."

"Work is going on, work will go on," he said, reiterating, "it's really something that's totally normal in this process."

In a statement Thursday, Minster of Transportation Steven Del Duca, suggested otherwise.

"Our government was elected on an ambitious plan to deliver an efficient and integrated transit system across the GTHA," Del Duca said.

"As such, we need certainty that everyone involved can deliver on the many components of this plan."