"Based on Justin's false statements at his news conference, and the fact that Canada is charging massive Tariffs to our U.S. farmers, workers and companies, I have instructed our U.S. Reps not to endorse the Communique", Trump wrote.
"He held a press conference and he said the U.S.is insulting".
The move enraged Trump, who branded his Canadian counterpart "dishonest and weak" in a furious tweet, announcing the USA would pull out of an agreed communique.
UK Prime Minister Theresa May told MPs on Monday that she wanted to pay "a particular tribute" to Mr Trudeau for his leadership and skilful chairing.
"I have made it very clear to the President that it is not something we relish doing, but it is something that we absolutely will do".
"They pay only a fraction of the cost - and laugh", he wrote, adding that the European Union needed to pay "much more" to help fund the global military alliance, which comprises 28 members including the UK, US, Germany, Canada and Turkey.
Enraged, our trading partners in North America, Europe and Japan say they will respond to our tariffs by levying their own on a wide range of goods and services produced in the United States. "Let us be serious and worthy of our people", Macron's office said in a statement obtained by Le Monde.
Hours after Trump withdrew his support for the joint statement and attacked Trudeau, White House economic advisor Larry Kudlow and trade adviser Peter Navarro drove the message home on Sunday morning news shows in an extraordinary assault on a close US ally and neighbor.
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U.S. President Donald Trump speaks during a news conference after his meeting with North Korean leader Kim Jong Un at the Capella Hotel on Sentosa island in Singapore June 12, 2018.
Nearly as an afterthought, Trump - now in Singapore for a summit with North Korean leader Kum Jong Un - tweeted: "Great to be in Singapore, excitement in the air!"
She left no doubt that European Union nations will impose counter-measures on United States goods in response, but cautioned against tit-for-tat retaliation which might lead to a trade war.
Members of Trump's inner circle continued the attacks, with both chief economic adviser Larry Kudlow - who said that Trudeau had "stabbed us in the back" - and Peter Navarro, Trump's trade adviser, directing a series of stinging comments at the Canadian leader.
"I think that those are words that I would not have chosen", Short said.
France is also standing by the G7 communique, a French presidency official said.
But Trump had already said he would not hesitate to shut countries out of the United States market if they retaliate against his tariffs. These countermeasures amount up to 16.6 billion Canadian dollars (about 12 billion USA dollars) in imports of steel, aluminum, and other products from the Unites States, and are set to come into effect on July 1 this year.
"Navarro himself crossed a line, basically telling a leader of a foreign nation that he needs to go to hell.I don't care how mad, how angry you are, you don't treat the head of state of another country like that unless you are getting ready for a military engagement of some kind".