The two-week-long Canadian truckers' protests against Covid rules threatens the country's economic recovery, ministers said, with growing demonstrations blocking a vital trade link with the United States.

More protesters have been joining the blockade of the Ambassador Bridge between Windsor and Detroit in solidarity with protests bringing the center of the capital Ottawa to a halt.

"We're all tired of this pandemic but these illegal blockades must stop," Industry Minister Francois-Philippe Champagne tweeted.

The suspension bridge, he noted, "is the most important land crossing in North America and is critical to our supply chains. 1000s of workers and businesses depend on it for their livelihoods."

More than 40,000 commuters, tourists and truck drivers carrying $323 million worth of goods travel across the span each day.

Scores of Canadian and American chambers of commerce and industry associations demanded the bridge is cleared, saying "as our economies emerge from the impacts of the pandemic we cannot allow any group to undermine the cross-border trade."

Another key trade link between Coutts, Alberta and Sweet Grass, Montana has also been clogged by protesters for several days.

'Freedom Convoy'

"This is a dramatic situation that is impacting the wellbeing of Canada's relationship with the United States and impacts immensely how business is able to conduct its operations," University of Ottawa professor Gilles LeVasseur told AFP.

He said that Ottawa and Washington must intervene.

"We're all tired, we're all frustrated" after two years of pandemic restrictions, Prime Minister Justin Trudeau told reporters in the capital, adding that Covid inoculations are "the way we're going to get to the other side."

More than 80 percent of Canadians have received two doses, while 50 percent of adults also got a booster.

The so-called "Freedom Convoy" began in January in western Canada -- launched in anger at requirements that truckers either be vaccinated, or test and isolate, when crossing the US-Canadian border.

Having snowballed into an occupation of the Canadian capital, the protest has sparked solidarity rallies across the nation and abroad.

Canadian Vehicle Manufacturers' Association president Brian Kingston warned that the Ambassador Bridge blockade was "threatening fragile supply chains already under pressure due to pandemic related shortages and backlogs."

Michelle Krebs, a senior analyst with Autotrader in Detroit, explained that North American assembly plants rely on timely parts deliveries across the suspension bridge.

The auto sector, she said, "is a significant portion of the economy and an important portion of consumer spending -- it's the second largest purchase people make -- and it's been hampered in the past year."

"We had felt we had hit the low point for inventories and production disruptions last October and we started seeing improvements, but this (protest) could be a setback if it lingers."

Canada's transport minister, Omar Alghabra, after hearing directly from automakers, warned Tuesday that the blockade could have "serious implications on our economy."

Covid rules easing

Several provinces this week announced a gradual lifting or loosening of Covid restrictions.

Saskatchewan went the furthest, saying it would end all checks on gatherings, as well as masking and vaccine requirements for indoor shopping and dining. Its premier, Scott Moe, said the benefits of Covid measures no longer outweighed the costs to society.

In the streets of Ottawa, hundreds of heavy trucks continued to block traffic and rev their engines, filling downtown with diesel fumes. A Canadian court on Monday ordered them to stop incessant honking that upset residents and made sleep difficult.

But, he added: "We have to see the same thing in other provinces now."

Politicians "are starting to realize that the Covid thing is wearing out," echoed fellow protester Mark Harrigan.