In this June 8, 2017, file photo, fresh nuts, bolts and fittings are ready to be added to the east leg of the pipeline near St. Ignace, Mich., as Enbridge prepares to test the east and west sides of the Line 5 pipeline under the Straits of Mackinac in Mackinaw City, Mich. THE CANADIAN PRESS/AP-Dale G Young/Detroit News via AP, File

In this June 8, 2017, file photo, fresh nuts, bolts and fittings are ready to be added to the east leg of the pipeline near St. Ignace, Mich., as Enbridge prepares to test the east and west sides of the Line 5 pipeline under the Straits of Mackinac in Mackinaw City, Mich. THE CANADIAN PRESS/AP-Dale G Young/Detroit News via AP, File

On eve of deadline, Canada makes case in court to keep Line 5 pipeline running

WASHINGTON — The federal government is stepping up its fight with Michigan over the fate of the Line 5 pipeline.

Natural Resources Canada filed court documents today to formally oppose Gov. Gretchen Whitmer’s effort to shut down the cross-border energy link.

Whitmer has given Calgary-based Enbridge Inc. until Wednesday to shut down Line 5 — a demand the company says it has no plans to meet.

Whitmer says she fears an environmental catastrophe in the Straits of Mackinac, the waterway where Line 5 traverses the Great Lakes.

A court-ordered negotiation is underway, with the two sides scheduled to meet again May 18, several days after Whitmer’s self-imposed deadline.

Canada’s so-called amicus brief urges the court to avoid a unilateral shutdown and expresses support for a mediated solution to the dispute.