US officials are urging the Canadian government to use its federal powers to end the truckers' protests over vaccine mandates, White House officials say.
President Joe Biden is "being regularly briefed" on the protests, which have hit Ottawa and a border crossing that generates a quarter of US-Canada trade.
Car-makers and local authorities are seeking an injunction to end the blockade of the Ambassador Bridge.
An Ontario court has stopped protesters from accessing online donations.
The truckers have raised over $US8 million ($NZ12m) through online platform GiveSendGo, after being kicked off GoFundMe for violating its policy on violence and harassment.
A statement from Ontario Premier Doug Ford, whose office pursued the order, said it "binds any and all parties with possession or control over these donations".
On Thursday, the US Secretaries of Homeland Security and Transportation, spoke to their Canadian counterparts "urging them to use federal powers to resolve this situation at our joint border and offering the full support of our Homeland Security and Transportation departments", the White House official said, according to CNN.
"We are principally focused on resolving the blockage at the Ambassador Bridge as well as other ports of entry," the official added.
The bridge remains closed to most traffic, however, other nearby ports and border crossings are open.
The Ambassador Bridge - now closed for four days - is the largest international suspension bridge in the world. It connects Windsor, Ontario, to Detroit, in the US state of Michigan.
Michigan Governor Gretchen Whitmer has also urged authorities to intervene, saying: "It's hitting paycheques and production lines. That is unacceptable."
The truckers have also been blockading the border checkpoint at Coutts, Alberta, next to the US state of Montana, for two weeks.
On Thursday, the protests spread to a third crossing at the border with the province of Manitoba and the US state of North Dakota.
Toyota, the world's biggest car manufacturer, has halted production at three factories in Ontario, saying no more vehicles will be produced there this week.
Output has also been halted at a Ford engine factory, while Stellantis, which owns Chrysler, said parts shortages had affected shifts at its Ontario plant.
On the other side of the border, General Motors said it had been forced to cancel two production shifts at a plant in Michigan where it builds sport utility vehicles.
Police receive fake emergency calls
Meanwhile, Ottawa authorities said on Thursday that 25 arrests have been made so far and 1775 tickets issued.
Residents have been advised to avoid non-essential travel and the city centre. A convoy of trucks drove slowly around the Ottawa International Airport for two hours on Thursday, in an effort to disrupt flights.
Ottawa police say their emergency call centres are being flooded with fake calls.
"They were coming in from the United States," Ottawa police chief Peter Sloly said in a news conference.
"Not exclusively, but significantly from United States addresses."
The demonstrations have proved to be a thorny issue for Liberal Prime Minister Justin Trudeau, who has faced calls to submit to some of the protesters' demands - including reversing the federal vaccine mandate on truckers entering Canada.
The Conservative opposition has called for all federal Covid-19 mandates to end.
But on Thursday, interim Conservative leader Candice Bergen, who has supported the truckers in recent weeks, changed her tune by calling for the protesters - whom she previously called "passionate, patriotic and peaceful" - to go home.
Bergen said her party would pursue the truckers' fight in the House of Commons.
The US Department of Homeland Security has said a copycat US protest may depart from California to Washington DC in the coming days.
They said the event has the potential to disrupt the Super Bowl, the final of the US National Football League, which is scheduled for Sunday in LA.
The agency's memo said the protests could continue into mid-March, and also disrupt President Biden's State of the Union address, scheduled for 1 March.
- BBC