Trump had earlier said that Russian Federation should be allowed back into the G8.
"They do so much more business with us than we do with them ... the numbers are so astronomically against them - we win that war a thousand times out of a thousand".
Here's a World Bank graph of trade-weighted average tariffs for the G7 countries - with United States almost identical to UK/Italy/France/Ger, higher than Japan/Can.
But foreign leaders publicly and pointedly rejected Trump's demands, raising the possibility of further escalation - particuarly after Trump's recently imposed tariffs on steel and aluminum from the European Union, Canada and Mexico and said doing so protected United States national security.
Canadian Prime Minister Justin Trudeau called USA metal tariffs "insulting" and announced retaliatory measures.
He also denied the summit had been contentious, a remark that contradicted what one G7 official described as an "extraordinary" exchange on Friday in which Trump repeated a list of trade grievances, mainly concerning the European Union and Canada. Trump has called for the full dismantling of that system over 10 years.
Trump has repeatedly bashed allies who sell more goods to the U.S. than they buy, though Europeans openly dispute his maths on trade deficits and insist their companies create U.S. jobs.
During the talks in Quebec, Trump surprised G-7 leaders by proposing an end to all tariffs and trade barriers.
On Saturday, Trump lapsed into his pre-summit rhetoric again, calling Trudeau "dishonest and week" in a fresh series of angry tweets.
Trump had run for the presidency on a vow to shrink the gaping US trade deficit - $566 billion previous year.
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Reneging on the commitments agreed in the communique showed "incoherence and inconsistency", it said in a statement. Angela and Emmanuel and Justin. You know, whether you like it or not, and it may not be politically correct, but we have a world to run. "That's what weak, dishonest Justin Trudeau did, and that comes right from Air Force One".
"If they retaliate they're making a mistake", he said.
Pierre Lampron, the president of Dairy Farmers of Canada, shot back at Trump's claims about his industry. "The prime minister said nothing he hasn't said before - both in public, and in private conversations with the president". "But he doesn't bring up the fact that they charge us up to 300% on dairy - hurting our Farmers, killing our Agriculture", the United States president said.
He described Trudeau's actions during the G7 as a "sophomoric play".
The pair have been at odds over whether a sunset clause would be included into any renegotiated trade agreement covering the US, Canada and Mexico, with Mr Trudeau insisting no sunset clause would be included and Mr Trump saying hours earlier that negotiators were "pretty close on the sunset provision".
Trump was reacting to comments made by Trudeau on Saturday in which he threatened to torpedo negotiations on a new NAFTA deal if the Americans did not remove tariffs on Canadian steel and aluminum.
"It was not contentious", Trump said. And tariffs are going to come way down, because people can not continue to do that.
Trudeau and the other G7 leaders used their meeting to try to persuade Trump to abandon the tariffs, which affect all of America's G7 allies.
Yet Buthe cautioned: "These kind of things can spiral out of control fairly quickly" as countries hammer each other with escalating retaliatory tariffs.
These tariffs, they told Trump, would hurt everyone.