Ford and Toyota companies have said they were halting some production as anti-coronavirus mandate protesters blocked U.S-Canada border crossings that have prompted warnings from Washington and Ottawa of economic damage.
Many pandemic-weary Western countries will soon mark two years of restrictions with similar protests spreading to Australia, New Zealand and France.
Horn-blaring protests have been causing gridlock in the capital Ottawa since late
January and from Monday night, truckers shut inbound Canada traffic at the Ambassador Bridge, a supply route for Detroit's carmakers and agricultural products.
Another border crossing, in Alberta province in Canada, has been closed in both directions since late on Tuesday.
More than two-thirds of the 511 billion US dollars in goods traded annually between Canada and the United States is transported by road.