WASHINGTON/OTTAWA/MEXICO CITY - US President Donald Trump said Monday that 25 percent tariffs on Mexico and Canada will take effect on Tuesday, March 4.

He told reporters at the White House it’s “very importantly” that the tariffs on Canada and Mexico will start Tuesday.

"What they have to do is build their car plants, frankly, and other things in the United States, in which case they have no tariffs," Trump said.

Trump also reiterated that the reciprocal tariffs will start on April 2.

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Canadian Prime Minister Justin Trudeau said Canada will impose 25 percent tariffs on 155 billion Canadian dollars (about $107 billion) worth of US goods if the US proceeds with its proposed tariffs on Canadian products.

Canada will begin with a 25 percent tariff on 30 billion Canadian dollars worth of US goods, immediately effective on Tuesday, followed by tariffs on the remaining 125 billion Canadian dollars of American products in 21 days' time, said Trudeau in a statement.

"Our tariffs will remain in place until the US trade action is withdrawn," he noted, adding that the Canadian government is in "active and ongoing discussions" with provinces and territories to pursue several non-tariff measures.

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On the same day, Canada's Ontario Premier Doug Ford said that his province is ready to cut off electricity and critical mineral supply to the United States in response to the expected US tariffs.

Ford, also the chair of the Council of the Federation of Canada's premiers, said Ontario is a major electricity exporter to the US states of New York, Michigan and Minnesota.

"If they want to try to annihilate Ontario, I will do anything, including cutting off their energy, with a smile on my face," he said.

Ford also threatened to halt exports of Ontario nickel during an interview with NBC News on Monday afternoon.

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"We will respond strongly and we don't want to," Ford said. "On the critical minerals I will stop shipments going into the US for nickel. I will shut down manufacturing because 50 percent of the nickel you use is coming from Ontario."

Ahead of Trump's announcement on Monday, Mexican President Claudia Sheinbaum, at her morning press conference, called for "temperance, serenity and patience" as the tariffs loomed, reassuring the public that her administration has multiple contingency plans in place.

Mexico has prepared "Plan A, Plan B, Plan C, and Plan D," the president noted, though she did not provide further details.

While she did not rule out direct communication with Trump, Sheinbaum emphasized that Mexico remains calm and prepared.

"Whatever his decision is, we will make our decisions, and there is a plan and unity in Mexico," she said.

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On Feb 1, Trump signed an executive order to impose a 25 percent tariff on imports from Mexico and Canada, with a 10 percent tariff increase specifically for Canadian energy products.

On Feb 3, Trump said the announced tariffs would be deferred for one month, allowing more time for negotiations. He has claimed that tariffs are intended to pressure the two US neighbors to intensify their efforts against fentanyl trafficking and curb illegal immigration.

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Both countries have taken steps to address his concerns. Trudeau said in his statement that Canada has appointed "a Fentanyl Czar", among other measures, to combat drug trafficking.

Mexico has ordered the deployment of 10,000 National Guard troops to its shared border with the United States to curb drug trafficking and mass immigration.