Sweeping U.S. tariffs on Canadian goods went into effect today after U.S. President Donald Trump dashed hopes of a reprieve on Monday.

Canada is retaliating with $30 billion in tariffs of its own, with an additional $125 billion in levies set to take hold after 21 days.

Click here to go straight to a recap of today’s tariff news. 

Prime Minister Justin Trudeau said in a press conference Tuesday morning that the U.S. has launched a “dumb” continental trade war and Canada is fighting back. He said that he will be meeting with the premiers Tuesday afternoon to talk about potential non-tariff responses.

Trudeau said the federal government will be there to support Canadians through measures like enhancing employment insurance “no matter the cost.”

Mexican President Claudia Sheinbaum said today her government would announce tariffs and other measures on Sunday in response to the U.S. duties and she expects to speak with Trump on Thursday.

Here is what is happening Day One of Trump’s tariffs:

• Trump mulling tariff relief for Canada, Mexico: Lutnick
• Trump mulling tariff relief for Canada, Mexico: Lutnick
• Trump mulling tariff relief for Canada, Mexico: Lutnick
• Trump mulling tariff relief for Canada, Mexico: Lutnick
• ‘This is going to be tough,’ PM warns Canadians
  This is going to be tough,’ PM warns Canadians
• Trump mulling tariff relief for Canada, Mexico: Lutnick
• Trump mulling tariff relief for Canada, Mexico: Lutnick
• This is going to be tough,’ PM warns Canadians
• Trump mulling tariff relief for Canada, Mexico: Lutnick
  This is going to be tough,’ PM warns Canadians
• This is going to be tough,’ PM warns Canadians
  This is going to be tough,’ PM warns Canadians
• This is going to be tough,’ PM warns Canadians
  This is going to be tough,’ PM warns Canadians
• This is going to be tough,’ PM warns Canadians
  This is going to be tough,’ PM warns Canadians
• This is going to be tough,’ PM warns Canadians
  This is going to be tough,’ PM warns Canadians
• This is going to be tough,’ PM warns Canadians

Click here to go straight to a recap of today’s tariff news. 

How did we get here?

Any possibility that tariffs on Canada and Mexico might be delayed or reduced was seemingly quashed Monday afternoon when Trump declared there was “no room left” to negotiate on the 25 per cent levies, which were originally announced in January.

“I would just say this to people in Canada or Mexico, if they’re going to build car plants, the people that are doing them are much better off building here because we have the market,” Trump said during a press conference.

Trump’s confirmation that the tariffs on Canada and Mexico would proceed — and that tariffs on China would be doubled to 20 per cent — sent stock markets tumbling, with the Dow Jones industrial average dropping close to 650 points and the S&P/TSX composite index falling nearly 400 points.

The development came after the U.S. Secretary of Commerce Howard Lutnick suggested earlier Monday on CNN that tariffs were not yet set in stone, and could be less severe than originally planned.

Which companies will be most impacted?

Potash miner Nutrien Ltd. is Canada’s most at-risk company when it comes to U.S.-imposed tariffs, according to a report from direct indexing platform Syntax Data.

The Saskatchewan-based company tops a list of the top 10 Canadian companies with the highest exposure to tariffs based on U.S.-generated revenue, using a proprietary classification system with data from 11,000 publicly listed companies.

The Syntax Data report says Nutrien’s customers could shoulder US$4.41 billion in additional costs from tariffs.

Four out of the top 10 at-risk firms identified in the report are energy production giants Enbridge Inc., TC Energy Corp., Suncor Energy Inc. and Parkland Corp.

The other most at-risk companies on the list based on tariff-impacted revenue are Magna International Inc. (US$10.85 billion), Barrick Gold Corp. (US$6 billion), Saputo Inc. (US$5.78 billion) and Bausch Health Companies Inc. (US$5.19 billion).

How is Canada responding?

Trudeau announced he would slap tariffs on $155-billion worth of U.S. imports, $30 billion of which would be immediate, with the remainder coming after 21 days.

On Monday, Ontario Premier Doug Ford announced Ontario would be taking U.S. alcohol off store shelves and would be ripping up a rural internet contract with Elon Musk’s Starlink.

Ford has also threatened cutting the power to 1.5 million U.S. homes.

Several other provinces have announced similar responses, primarily pledging to pull U.S. liquor from store shelves and to review government contracts with U.S. companies, though Alberta’s government doesn’t believe in retaliatory tariffs.

Tariffs live blog

With files from Financial Post staff, The Canadian Press and Bloomberg News