And now, Morneau added the tariffs to Canada's list of deal breakers on NAFTA.
Despite being at odds with other countries at the G7 in Canada, Trump rated his relationship with their leaders as a "10" - naming Germany's Angela Merkel, French president Emmanuel Macron and Canada's Justin Trudeau, but not the UK's Prime Minister Theresa May.
Trump's administration last week ended a two-month exemption to steel and aluminum imports from Mexico, Canada and the European Union.
He added, "if they retaliate, they're making a mistake. Or we'll stop trading with them".
Trump told reporters in Quebec before leaving the Group of Seven summit that he "came up with the term fake news" because much of the USA press "is very dishonest".
The furious United States president, speaking in Quebec, Canada, said the USA had been "taken advantage of for decades and decades" by the res too the world.
Trump also suggested that Friday and Saturday's summit had been "very, very successful", and dismissed claims of tensions between the USA and other nations, describing their relationship "a 10".
Trump insisted U.S. allies would yield to his demands of a trade rebalance, warning that the USA would crush any opposition in a potential trade war.
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Trump called the summit a "one time shot" for Kim, but expressed optimism at the beginning of talks with the North Korean regime.
"The simple fact is that more trade has been overwhelmingly beneficial to USA families and to net USA job creation for 75 straight years, and pretending America has been taken advantage of - that is, pretending that we're losers - isn't true".
Donald Trump said "we can't do that anymore" and said it was time for the USA to be treated better by the EU, Canada and other trading partners not represented at the summit.
In response, Canada, Mexico and the European Union said they were putting in place their own retaliatory measures.
But a grinning Trump answered for him: "He's happy", he cracked.
When a CNN reporter asked Trump about anger and frustration from U.S. allies over trade, he lambasted the reporter and his "fake friends at CNN".
President Donald Trump has opened his second day at an global summit at a breakfast discussion on gender equality. Trump said as he departed the White House for the summit in Quebec.
Trudeau had made the issue of gender equality a priority for the gathering.
"Looking forward to straightening out unfair Trade Deals with the G-7 countries".
A French official, speaking to the Reuters news service on background, said the seven countries were likely to produce a joint communiqué but the final text would make clear that on topics such as the environment, the United States did not share the point of view of the other six members.