The attorney general, David Eby, told reporters that British Columbia is approving Trans Mountain permits on the same timeline as other major projects, and that its new environmental rules and a jurisdictional challenge simply come down to the province protecting its interests.

"It is not to stop the pipeline, it is not to prevent it - it's to ensure that we have the protections in place for when the pipeline is built and turned on," Eby said.

His comments run up against assertions from Kinder Morgan, which stopped all non-essential work on the C$7.4 billion ($5.8 billion) project last month, citing permitting delays and political opposition in British Columbia, and set a May 31 deadline to decide if the build would go ahead or not.

Alberta's premier, Rachel Notley, said separately that her province was "getting closer" in its talks with Kinder Morgan to ensure the expansion gets built, but she declined to provide details.

Notley backed out of a meeting with other Western Canadian provincial leaders this week, including B.C. Premier John Horgan, saying she would instead focus on Trans Mountain as the May 31 deadline looms.

Canadian oil trades at a steep discount to the North American benchmark, with the gap widening in recent months due to tight capacity on rail and pipelines.

That has Alberta desperate to get new pipelines built, particularly a line to the coast to access overseas markets. The Trans Mountain expansion would nearly triple capacity on an existing line from Alberta to a Metro Vancouver port.

The project is fiercely opposed by environmental groups, some aboriginal groups and the B.C. government.

B.C. said on Tuesday that it had filed a challenge to a new Alberta law that would allow the oil-rich province to cut fuel shipments west.

(Reporting by Julie Gordon in Vancouver; Editing by Leslie Adler)