Ottawa, Canada - The era of deep economic, security, and military ties between Canada and the US "is over," Prime Minister Mark Carney said Thursday after President Donald Trump announced steep auto tariffs.

Trump's planned 25% levy on vehicle imports to the US is to come into force next week and could be devastating for a Canadian auto industry that supports an estimated 500,000 jobs.

After Trump's announcement, Carney paused his campaign ahead of Canada's April 28 election to return to Ottawa for a meeting of cabinet members working on tactics in the trade war with the US.

He called Trump's auto tariffs "unjustified," and said they were in breach of existing trade deals between the countries.

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He also warned Canadians that Trump had permanently altered relations with the US and that, regardless of any future trade deals, there would be "no turning back."

"The old relationship we had with the United States based on deepening integration of our economies and tight security and military cooperation is over," Carney said.

He said Canada would retaliate against the auto tariffs.

"Our response to these latest tariffs is to fight, is to protect, is to build," Carney said.

"We will fight the US tariffs with retaliatory trade actions of our own that will have maximum impact in the United States and minimum impacts here in Canada," he added.

Carney replaced Justin Trudeau as prime minister on March 14.

Typically, a new Canadian leader makes a phone call with the US president a priority immediately after taking office, but Trump and Carney have not spoken.

He said Thursday that the White House had reached out to schedule a call and that he expected to speak to Trump in the "next day or two."

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Carney has also said that while he is willing to talk to Trump, he will not participate in substantive trade negotiations with Washington until the president shows Canada "respect," particularly by ending his repeated annexation threats.

"For me, there are two conditions, not necessarily for a call, but a negotiation with the United States. First Respect, respect for our sovereignty as a country... apparently it's a lot for him," Carney said.

"There has to be comprehensive discussion between the two of us, including with respect to our economy and our security," he added.