Canadian leaders on both the ideological left and right are promising to start an economic war with America after President Trump threatened their country with even higher tariffs on Tuesday, saying he would ratchet up his 25 percent tariff to as high as 50 percent following Prime Minister Trudeau’s imposition of 25 percent tariffs on more than $100 billion worth of American goods. 

The president’s 25 percent tariffs on both Canadian and Mexican goods took effect at midnight Tuesday after Mr. Trump insisted that neither country was doing enough to combat the trafficking of fentanyl across their borders into America, despite the billions of dollars both are now investing in border security measures. Mr. Trudeau claims that the American tariffs aren’t about fentanyl at all, however. 

“What he wants to see is a total collapse of the Canadian economy because that’ll make it easier to annex us,” the prime minister said. “That’s never going to happen. We will never be the 51st state.”

Following a press conference during which Mr. Trudeau announced the 25 percent tariffs, Mr. Trump issued another threat on Truth Social: “Please explain to Governor Trudeau, of Canada, that when he puts on a Retaliatory Tariff on the U.S., our Reciprocal Tariff will immediately increase by a like amount!” the president said.

The premier of Ontario, Doug Ford, is following his prime minister’s lead with the aggressive economic punishments. Mr. Ford said Tuesday that he would bar American companies from Ontario’s procurement contracts, which will cost American firms tens of billions of dollars in government work. He said Monday that he would also be willing to “cut off” America from his province’s energy supplies, and that he would do so with a smile on his face.

Mr. Ford announced that he would follow through with his promise to cancel all provincial contracts with Elon Musk’s own telecommunications company, Starlink. 

“It’s done, it’s gone,” Mr. Ford said of the contract with Mr. Musk. “We won’t award contracts to people who enable and encourage economic attacks on our province and our country.”

“They only have President Trump to blame,” the premier said, echoing comments by the prime minister that American consumers should levy their grievances with Mr. Trump. 

The threat of a one-two punch to the Canadian economy could have serious effects not just for the bilateral relationship, but for Canada’s politics as well.

Mr. Trudeau announced earlier this year that he would step aside and not lead his party in the next federal election, which is due to take place in October. Before Mr. Trump took office, the Conservative Party was on track to sweep an overwhelming majority of the seats in the House of Commons. The opposition party’s leader, Pierre Poilievre, has seen his star dim with Mr. Trump dominating their national politics, however. 

According to recent polling from Nanos Research, Mr. Trudeau’s liberal party now trails the Conservatives by just two points nationally — a far cry from the 25-point lead Conservatives held late last year, just before Mr. Trump won the presidential election.

The White House’s explanations for why the tariffs are necessary have also been shifting. On Tuesday, Mr. Trump claimed that part of the reason he was taking action was because American banks aren’t able to operate in Canada, even though more than a dozen banks with more than $100 billion in assets are operating in the country. 

“Canada doesn’t allow American Banks to do business in Canada, but their banks flood the American Market. Oh, that seems fair to me, doesn’t it?” the president wrote on Truth Social. Mr. Trudeau, at his press conference, pointed out that those claims were untrue. 

“[There are] 16 American banks currently operating in Canada holding about $113 billion worth of assets in this country, so American banks are alive and well and prospering in Canada. It’s an example of not really being able to see what he wants, because even the excuse he’s giving for these tariffs today — fentanyl — is bogus,” Mr. Trudeau said. 

On Monday night, after Mr. Trump insisted that he was not letting up in his original threat to implement the tariffs, Mr. Trudeau said he would hit back with a narrower tariff scheme that will get worse in the coming weeks. 

“Canada will be implementing 25 percent tariffs against $155 billion worth of American goods, starting with tariffs on $30 billion worth of goods immediately, and tariffs on the remaining $125 billion of American products in 21 days,” the prime minister said at his press conference Tuesday. The $155 billion is in Canadian dollars, meaning the amount is similar to just over $100 billion U.S. dollars. 

“I want to speak directly to one, specific American: Donald,” Mr. Trudeau said, flanked by members of his government. “This is a very dumb thing to do. We two friends fighting is exactly what our opponents around the world want to see.”