The United States and Canada have swung sharply toward a diplomatic and trade crisis as top White House advisers lashed out at Canadian Prime Minister Justin Trudeau a day after US President Trump called him "very dishonest and weak."
The spat drew in Germany and France, which sharply criticised Trump's decision to abruptly withdraw his support for a Group of Seven communique hammered out at a Canadian summit on Saturday, accusing him of destroying trust and acting inconsistently.
"Canada does not conduct its diplomacy through ad hominem attacks ... and we refrain particularly from ad hominem attacks when it comes to a close ally," Canadian Foreign Minister Chrystia Freeland told reporters.
Trump, who is in Singapore for the summit with North Korean leader King Jong Un, escalated his war of words with Canada and the European Union in a pair of tweets.
"Fair Trade is now to be called Fool Trade if it is not Reciprocal" Trump said and suggested that Canada was profiting from US trade, citing what he said was a Canadian press release. "Then Justin acts hurt when called out!"
He again suggested the US was footing too much of the costs of NATO and "protecting many of these same countries that rip us off" on trade. The European Union, he added "should pay much more for Military!"
On Sunday, White House economic adviser Larry Kudlow accused Trudeau of betraying Trump with "polarising" statements on trade policy that risked making the US leader look weak ahead of the historic summit with Kim.
"(Trudeau) really kind of stabbed us in the back," Kudlow, the director of the US National Economic Council, said on CNN.
Trade adviser Peter Navarro separately told Fox News Sunday "there is a special place in hell for any leader that engages in bad faith diplomacy" with Trump.
Trudeau's office said he had not said anything in his closing G7 news conference he had not said to Trump before.
The majority of Canadian exports go to the US, making Canada uniquely vulnerable to a US trade war.
Trudeau got direct personal support from European leaders.
British Prime Minister Theresa May "is fully supportive" of Trudeau and his leadership, a senior UK government source said, while European Council President Donald Tusk tweeted: "There is a special place in heaven for @JustinTrudeau."
Freeland, asked about support from allies, said: "The position of our European allies, including Japan, is the same as ours. We coordinated very closely with the European Union, with Mexico, on our list of retaliatory measures and actions."
Europe will implement counter-measures against US tariffs on steel and aluminium just like Canada, German Chancellor Angela Merkel said, voicing regret about Trump's decision to withdraw support for the communique.
Trump's backing out of the joint communique torpedoed what appeared to be a fragile consensus on a trade dispute between Washington and its top allies.
Trump also said he might double down on import tariffs by hitting the sensitive auto industry, throwing the G7's efforts to show a united front into disarray.
Meanwhile, South African President Cyril Ramaphosa, who met with Trudeau on Sunday, said it was time for G20 nations to play a role and to "also bring about some good sense to all the key players."