The import bans, which go into effect on September 29 and were published on the White House's website, came after Canada's retaliatory tariffs on US goods took effect after midnight on Tuesday.
Those Canadian levies themselves followed 50 per cent tariffs that the United States imposed on some $US20 billion ($A28 billion) of Canadian goods in August, after several rounds of negotiations collapsed.
The breakdown has widened a rift between the longtime allies, both of whom have blamed the other for the failed talks, and spurred Canadian Prime Minister Mark Carney to urge a further shift away from the country's biggest trading partner.
"We have everything we need to pivot and prosper," Carney said on Tuesday in a video posted on YouTube after the tariffs came into effect.
"That pivot will come at a cost. There's always a cost to action. But it doesn't come close to the cost of standing still," he said.
Ottawa designed the retaliatory measures to put economic and political pressure on Washington, Canadian government officials said, and the tariffs are expected to hit sectors in some competitive states such as Michigan and Ohio, ahead of US midterm elections in November.
Gabriel Brunet, spokesperson for Dominic LeBlanc, Canadian minister responsible for bilateral US trade, said: "Canadian and American officials have maintained ongoing discussions on a range of issues, although formal trade negotiations are not taking place at this stage."
Ottawa's counter-tariffs cover some $US20 billion of US goods, with duties ranging from 15 per cent to 50 per cent across products from steel and furniture to clothing and electronics.
While the new tariffs affect a small amount of exports compared with total trade between the US and Canada, some analysts worry the standoff could destabilise the US-Mexico-Canada Agreement, the free-trade pact that succeeded NAFTA. Together they have underpinned commerce across North America for decades.
Trump's social media posts, which targeted Canada over the long holiday weekend, continued into Monday when he attacked Canada's procurement policies.
In a post on Truth Social, Trump directed the General Services Administration to "REMOVE Canadian-origin products from GSA's Multiple Award Schedules unless Canada restores full and fair reciprocity for American Farmers and Companies."
On Monday, Trump said Canadian private jet maker Bombardier would no longer be allowed to sell its planes in the US unless it started manufacturing in the country, without saying whether an official government order would follow. The company's shares opened down more than six per cent on the Toronto Stock Exchange on Tuesday.
The Bombardier post followed another Trump post where he shared a map of North America draped in the US flag, including Canada and Mexico.
He also shared an AI-generated image reviving a running jab at Carney, calling him "Governor," a reference to his repeated taunt that Canada should become the 51st US state.
Trump's tariffs hit sectors including wine, furniture, dairy products, cement, clothing, fishing rods and hockey equipment, covering $US20 billion, or five per cent, of Canadian exports to the US.
with dpa
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