Trump fired back after Trudeau's press conference, blasting the Canadian leader on Twitter as "very dishonest and weak".
"Our Tariffs are in response to his of 270% on dairy!" the US president tweeted.
Before leaving for Singapore, Mr. Trump had delivered a stark warning to America's trading partners not to counter his decision to impose tariffs on steel and aluminum imports. "He really, actually, you know what, he did a great disservice to the whole G-7".
May 31 - The Trump administration announces that Canada will no longer be exempt from steel and aluminum tariffs, prompting the Trudeau government to announce its own counter-measures.
"For Canadians who ... stood shoulder to shoulder with American soldiers in far-off lands and conflicts from the First World War onward.it's kind of insulting", Trudeau said.
Trump continued tweeting Sunday evening about Trudeau, accusing Canada of making $100 billion in trade with the U.S.
"[Trudeau] went out of his way to try to downplay tensions", said White House reporter Michael Shear. At one point he wrote, "Justin acts hurt when called out!"
The remarks apparently upset Trump, who had left the conference early to travel to Singapore for a highly anticipated meeting with North Korean leader Kim Jong-un.
Trump "did the courtesy to Justin Trudeau to travel up to Quebec for that summit".
In a pointed criticism of Trump's policy, May said that the most effective way of reaping the benefits of globalisation was through multilateral action, adding: "It can not be done by taking unilateral action against your partners".
Beyond the bilateral meetings, the G7 leaders took part in two working groups whrre discussion of trade was front and centre.
"Canada does not conduct its diplomacy through ad hominem attacks. and we refrain particularly from ad hominem attacks when it comes from a close ally", Freeland told reporters in Quebec City on Sunday.
Former prime minister Stephen Harper also shared his perspective on the trade spat between Canada and the U.S. Harper said that although he could understand the United States wanting better trade relations with countries like China and Mexico, he can't "understand the obsession with trade relations with Canada".
After Kudlow's comments, Trump added to his string of criticisms against Canada in a series of tweets on Sunday night.
- Donald J. Trump (@realDonaldTrump) June 9, 2018Fair Trade is now to be called Fool Trade if it is not Reciprocal.
Similarly, Krueger said Trump was unlikely to take the countermeasures lying down and could hit back with more trade restrictions.
She said that the European countries will not be "taken advantage of" in terms of trade and that they would "act" against the USA trade measures, which are considered as going against the World Trade Organization's rules.
"Fair trade is now to be called fool trade if it is not reciprocal", he wrote in one tweet that then went on to accuse Canada of imposing unfair taxes on U.S. dairy products.
White House economic adviser Larry Kudlow accused Trudeau of betraying Trump with "polarizing" statements on trade policy that risked making the us leader look weak ahead of a historic summit with North Korean leader Kim Jong Un.