Canada’s Ontario province has declared a state of emergency and Premier Doug Ford threatened fines and jail terms as authorities come under increasing pressure from the US to end anti-vaccine mandate protests that have drastically cut trade between the two countries.

The “Freedom Convoy” by Canadian truckers opposing a vaccinate-or-quarantine mandate for cross-border drivers, mirrored by the US government, began with the occupation of the Canadian capital Ottawa.

Truckers then blocked the Ambassador Bridge earlier this week and shut down two other smaller border crossings.

The closure of the bridge, North America’s busiest international land border crossing and a key supply route for Detroit’s car makers, has halted some vehicle output and left officials scrambling to limit economic damage.

“I will convene cabinet to use legal authorities to urgently enact orders that will make crystal clear it is illegal and punishable to block and impede the movement of goods, people and service along critical infrastructure,” Mr Ford said on Friday (local time).

Ford also pledged new legal action against protesters, including fines and potential jail time for non-compliance with the government’s orders.

Michigan Governor Gretchen Whitmer said on Friday she had been pushing the Canadian government to get the protest under control and that the bridge blockade was hurting her state.

“The Canadian government has to do whatever it takes to safely and swiftly resolve this,” Ms Whitmer told CNN.

US President Joe Biden’s administration on Thursday urged Canada to use federal powers to ease the disruption.

Canadian Prime Minister Justin Trudeau said he was working with municipal leaders to end the blockade.

Public Safety Minister Marco Mendicino said federal police forces would be deployed to Windsor, near the bridge, and to Ottawa.

Mr Mendicino was scheduled to speak to US Homeland Security Secretary Alejandro Mayorkas on Friday, his office confirmed.

Police in Windsor, Ontario, which borders Detroit, said they had received additional resources from outside jurisdictions to “support a peaceful resolution to the current demonstration at and near the Ambassador Bridge”.

In Ottawa, the epicentre of the protests, police were waiting on Thursday for a request for provincial and federal reinforcements to be completed.

They have made 25 arrests so far.

City police chief Peter Sloly expected the reinforcements to arrive within 48 hours, ahead of a potential rise in protesters in the city at the weekend.

“This is an entirely sophisticated level of demonstrators. They have the capability to run strong organisation here provincially and nationally, and we’re seeing that play out in real time,” Mr Sloly said.

Canada sends 75 per cent of its exports to the US and the Ambassador Bridge usually handles 8000 trucks a day, representing a quarter of all cross-border trade, or about C$500 million ($548.76 million) per day.

About C$100 million worth of car parts cross the border each day, with many shipments timed to arrive just as manufacturers need them.

General Motors, Ford Motor, Chrysler parent Stellantis and Toyota Motor Corp have been affected by the blockades.

While officials at the federal, provincial and municipal levels have met regularly, they have had limited impact on the ground.

Windsor Mayor Drew Dilkens has sought an injunction from the Ontario Superior Court to have the protesters at the bridge removed, adding that he was striving to resolve the issue peacefully and ensure that nobody got hurt.

Canadian Health Minister Jean-Yves Duclos said the government was reviewing its pandemic-related border restrictions and would likely announce changes next week.

“With the worst of Omicron now behind us, our government is actively reviewing the measures in place at our borders and we should be able to communicate changes on this next week,” he said.

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