In a press conference Saturday after a contentious G7 meeting, Trudeau said that Canada had been insulted by the Trump administration's tariffs and that his country would go ahead with its own retaliatory measures by July 1.
Mr Trump responded by tweeting en route to his next summit, in Singapore, that he had instructed USA officials "not to endorse the communique as we look at tariffs on automobiles".
American President Donald Trump has said the WTO has been a "disaster" and "very unfair" towards the United States.
Mr Trudeau did not respond to questions about Mr Trump when the prime minister arrived at a Quebec City hotel on Sunday for meetings with other world leaders, though Mr Freeland later told reporters that "we don't think that's a useful or productive way to do business". That was a part of Trudeau's mistake.
A top US White House advisor has accused Canadian Prime Minister Justin Trudeau of stabbing the US in the back.
"Here's the thing. "He really kind of stabbed us in the back".
White House trade adviser Peter Navarro said Sunday that there is a "special place in hell" for leaders like Canadian Primer Minister Justin Trudeau who, Navarro said, had engaged in "bad diplomacy".
The President's move to reject the communique followed a statement from Trudeau earlier, in which the prime minister announced, "We have released a joint communique by all seven countries" indicating that the United States had signed on.
Trade ministers and politicians from multiple countries have voiced opposition in the media to the tariffs ahead of the G-7 summit, and have indicated they may band together to push the US president to reverse his decision.
The chancellor also addressed concerns that Trump would hit back by implementing tariffs on German vehicles, saying, "First of all, we'll try and see if we can prevent this".
"On the issue of [tariffs and trade deficits] alone, we have allies strategically, but when it comes to trade disputes, these allies are basically robbing us blind", he said. He described all seven leaders coming together to sign the joint declaration despite having "some strong, firm conversations on trade, and specifically on American tariffs".
French President Emmanuel Macron said "international co-operation can not be dictated by fits of anger and throwaway remarks".
The G7 meeting in Canada was complicated and disappointing, but the format should be preserved, German Chancellor Angela Merkel said Sunday.
Bizarrely, Trump admitted that he levied the tariffs in response to Canadian dairy protections - not for security reasons - and yet he called Trudeau a liar.
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