A Canadian province says it will join the legal challenge against the Kinder Morgan pipeline.
Environment Minister George Heyman said the pipeline is not in the "best interest" of British Columbia at a press conference on Thursday.
The Trans Mountain extension would connect Alberta to British Columbia and triple Kinder Morgan's capacity.
The project was approved by Prime Minister Justin Trudeau in November, and has been touted by Donald Trump.
But it still faces a number of hurdles, including a legal challenge by British Columbia's First Nations.
"We are committed to use every tool to defend BC's coast," said Mr Heyman during the press conference, where he was joined by the province's attorney general.
The province will retain council, and seeks to become an official intervener during future Kinder Morgan hearings.
Mr Trudeau has said the pipeline is in the national economic interest and part of his plan to transition to cleaner energy. It was supported by British Columbia's former BC Liberal premier, Christy Clark who was ousted in June by NDP Leader John Horgan.
Mr Horgan had promised throughout his campaign to fight the pipeline. Although he lost a minority government by a slim margin, he was able to wrest power from Ms Clark by forming a coalition with the anti-pipeline BC Green Party.