CALGARY, Alberta—Enbridge Inc. asked the Canadian government on March 16 to champion its Line 5 oil pipeline in a legal battle with the State of Michigan, which is trying to shut down the pipeline over concerns it could leak into the Great Lakes.

Calgary-based Enbridge is also asking Ottawa to provide support for its U.S. federal court filings on Line 5, Vern Yu, Enbridge executive vice president of liquids pipelines, told a federal parliamentary committee.

The dispute between Enbridge and Michigan has escalated as a May deadline to shut down the 540,000-barrel-per-day pipeline looms closer.

Line 5 is a key part of the Enbridge pipeline network supplying refineries in eastern Canada and the U.S. Midwest with western Canadian crude. Leaders in both countries are trying to reduce their economies’ dependence on fossil fuels, although Canada is supporting the ongoing operation of Line 5, especially after U.S. President Joe Biden canceled permits for the cross-border Keystone XL pipeline project.

Late last year, Michigan Gov. Gretchen Whitmer ordered Line 5 to cease operating by May over concerns a 4-mile section running along the lakebed of the Straits of Mackinac could leak.

Enbridge is challenging that order in U.S. federal court, and the company has proposed building a $500 million underwater tunnel to protect the pipeline beneath the Straits.

Canadian Prime Minister Justin Trudeau’s Liberal government has already said it will look at all options to keep Line 5 operating, including invoking the 1977 Transit Pipelines Treaty.

“We request the government of Canada use every pathway to assert that Line 5 is an important binational pipeline protected by the treaty, whose shutdown would have grave impacts for both the United States and Canada,” Enbridge’s Yu said.

Enbridge does not expect the pipeline will be forced to shut down in May, Yu said, because Michigan needs a court injunction to enforce its order. He added, however, that court battles over the pipeline could go on for “many, many” years.

“I think it’s essential that we try to come up with a mediated, negotiated diplomatic solution that takes us out of the hands of the court and provides a reasonable outcome for everyone involved,” Yu said.

Enbridge and Michigan had their first meeting with a court-appointed joint mediator last weekend, Yu said, but he declined to comment on how that went.