From Singapore, where he is set to hold a historic summit with North Korean leader Kim Jong Un, he unleashed a volley of angry tweets targeting the European Union, Canadian Prime Minister Justin Trudeau and NATO allies, including Germany.
"I have made it very clear to the President that it is not something we relish doing, but it something that we absolutely will do", Trudeau said.
Just as the G7 meeting of the world's leading industrialised nations had seemed to weather Mr Trump's threats of a trade war, the president backed out of the group's joint statement that Mr Trudeau said all the leaders had come together to sign.
Trump quickly fired back on Twitter, calling Trudeau's comments "very dishonest and weak".
In a matter of hours and series of texts, the US has rushed into a diplomatic crisis with its closest allies, adding anxiety to an already tense global economy.
Trump advisers also took up the attack in appearances on Sunday's news shows, leveling more withering and unprecedented criticism against Trudeau, branding him a back-stabber unworthy of Trump's time.
Toyota Motor to invest USD1 billion in ride-hailing firm Grab
Grab called it the largest-ever investment globally by an automotive manufacturer in the ride-hailing sector. Grab said it logs six million rides a day via apps downloaded onto over 100 million mobile devices.
Before the apology, some US lawmakers on Tuesday questioned the strong language the White House and Trump have used toward Canada in contrast to the praise he gave North Korea at Tuesday's summit in Singapore.
Foreign Affairs Minister Chrystia Freeland said Sunday that "Canada does not believe that ad hominem attacks are a particularly appropriate or useful way to conduct our relations with other countries". He learned. That's going to cost a lot of money for the people of Canada.
Trump's tough rhetoric for the leader of Canada, one of the United States' closest allies, was in sharp contrast with the words he chose to describe Kim.
Trudeau promised retaliatory measures against US tariffs on Saturday evening after the summit, a move Navarro called "nothing short of an attack on our political system".
Mr Trudeau said he had reiterated to Mr Trump, who left the G7 meeting before it ended, that tariffs would harm industries and workers on both sides of the US-Canada border.
The Office of the United States Trade Representative's notes that the United States had an $8.4 billion trade surplus with Canada in 2017.
Committee Chairman Bob Corker, R-Tenn., said Tuesday that he's "glad" that Navarro admitted that he misspoke.