US-CANADA trade is being damaged by a Canadian trucker anti-vaccine mandate blockage of the Ambassador Bridge between Detroit and Windsor, reports the American Journal of Transportation.

The Ambassador Bridge accounts for 30 per cent of total Canada-US trade. Up to US$500 million in goods cross it every day, carried by 8,000 to 10,000 trucks.

The crisis has reached the point of being followed closely at the White House, with Michigan Governor Gretchen Whitmer raising the alarm.

The surprise blockade movement began when the truckers' "Freedom Convoy" clogged Canada's capital, Ottawa to protest the government's move to require that Canadian truck drivers crossing the US border be fully vaccinated.

It has since broadened to protest all vaccination mandates.

Governor Whitmer declared the protest is hurting "Michigan's working families who are just trying to do their jobs,"

Canada is Michigan's top customer, and Michigan sells more to Canada than to its next eight largest foreign markets combined.

"It is imperative that Canadian local, provincial and national governments de-escalate this economic blockade," said Ms Whitmer.