The Biden administration urged Prime Minister Justin Trudeau’s government Thursday to use its federal powers to end the truck blockade by Canadians protesting the country’s Covid-19 restrictions, as the bumper-to-bumper demonstration forced auto plants on both sides of the border to shut down or scale back production.

For the fourth straight day, scores of truckers taking part in what they dubbed the Freedom Convoy blocked Ambassador Bridge connecting Windsor, Ontario, to Detroit, disrupting the flow of auto parts and other products between the countries. The White House said Homeland Security Secretary Alejandro Mayorkas and Transportation Secretary Pete Buttigieg spoke to Canadian counterparts and urged them to help resolve the standoff.