The US government has urged Canada to use federal powers to ease the growing economic disruption caused by the blockade of the vital Ambassador Bridge by protesters opposed to coronavirus mandates.

The closure of North America’s busiest international land border crossing, a vital supply route for Detroit’s carmakers, has halted some auto output and left officials scrambling to limit economic damage.

Canadian truckers started their protests as a “Freedom Convoy” occupying Ottawa, the capital, to demonstrate opposition to a vaccinate-or-quarantine mandate for cross-border drivers mirrored by the US government.

They began blocking the Ambassador Bridge on Monday and have since shut two smaller border crossings in Alberta and Manitoba provinces.

As many pandemic-weary western countries near the two-year mark on coronavirus restrictions, copycat protests have spread to Australia, New Zealand and France, although the wave of infections caused by the highly infectious Omicron variant has begun to subside in some places.

The US homeland security secretary, Alejandro Mayorkas, and the transportation secretary, Pete Buttigieg, urged their Canadian counterparts “to use federal powers to resolve this situation at our joint border”, a White House official said on Thursday.

“US and Canadian border and customs authorities are working with great urgency to ensure the continued flow of goods and services across our international border, leveraging alternative land routes, as well as air and sea options.”
The US homeland security adviser, Liz Sherwood Randall, was due to speak with the Canadian deputy minister of national defence, Jody Thomas.

Canadian federal ministers have called the blockade illegal and asked protesters to return home. Police near the Ambassador Bridge had begun receiving additional manpower, said Drew Dilkens, the mayor of Windsor, Ontario, which borders Detroit.

“[If] the protesters don’t leave, there will have to be a path forward,” he told CNN. “If that means physically removing them, that means physically removing them, and we’re prepared to do that.”

Dilkens later said Windsor was seeking an injunction from Ontario superior court to have the protesters removed, adding he was striving to resolve the issue peacefully.

“It may be gratifying for someone to see the forced removal of the demonstrators, [but] such action may inflame the situation and certainly cause more folks to come here and add to the protest, and we don’t want to risk additional conflict,” Dilkens said.

With traffic at times shut in both directions, General Motors and Chrysler’s owner Stellantis said on Thursday they had to cancel or reduce shifts because of parts shortages, tacking on to earlier production cuts announced by Ford and Toyota.

Toyota said it was suspending production through Saturday at its plants in Ontario and Kentucky, affecting manufacturing of the Camry, RAV4 and other popular models.

Ford was looking at flying in some auto parts to a plant in Windsor that produced engines for popular models, a union official said.

The Canadian prime minister, Justin Trudeau, said he was working to end the bridge blockade, which hurt “regular Canadians whether it’s grocery store prices, whether it’s jobs lost or suspended, whether it’s supply chains disrupted”.

An Ontario court on Thursday froze funds donated to anti-vaccine protesters through the app GiveSendGo. The convoy group had raised more than $8m as of late Thursday afternoon, the Boston-based company said.

Protesters began gathering with their vehicles in Ottawa nearly two weeks ago and have occupied the main downtown street that runs by parliament, the Bank of Canada and the prime minister’s office.

More than two-thirds of the $511bn in goods traded annually between Canada and the US is transported by road. The Detroit International Bridge Company, which owns the Ambassador Bridge, urged Canada to end the protest by repealing the vaccine mandate or removing the vehicles.

A third option was to do “nothing and hope this ends on its own – an option that will most likely prolong the blockade, further crippling our economy and putting more jobs at risk”, said the company’s chairman, Matt Moroun.

Seeking to show support for the Canadian protesters, some US truckers said they would send two convoys this weekend to a fourth border crossing that connects Buffalo, New York, and Fort Erie, Ontario.

The US was adding staff to its command post at the National Football League’s Super Bowl in Los Angeles in response to reports of a convoy causing disruptions at Sunday’s game, the White House official said.

The Department of Homeland Security was making preparations to ensure that a Freedom Convoy event in Washington DC due in early March “does not disrupt lawful trade and transportation or interfere with federal government and law enforcement operations and emergency services”, the official said.