Mr. Trump's tweets taking aim at the leader of a country that has always been a U.S. ally came after the President left the G7 summit in Canada to travel to Singapore ahead of a planned diplomatic meeting with North Korean Leader Kim Jong-un, CNN reported.
Kudlow had been negotiating nicely with Trudeau at the summit in Quebec and the U.S. had agreed to join the joint communique, but Trump pulled out after he felt betrayed by Trudeau's news conference where the prime minister called Trump's tariffs on Canadian aluminum and steel exports "insulting".
Trump tweeted from Singapore where he traveled for a summit with North Korean leader Kim Jong Un after attending a meeting of G-7 leaders in Canada.
"In a matter of seconds, you can destroy trust with 280 Twitter characters", German Foreign Minister Heiko Maas said when asked about Trump's decision.
In response, Canada, Mexico and the European Union said they were putting in place their own retaliatory measures.
Guy Verhofstadt, a former Belgian prime minister who as an MEP now co-ordinates Brexit talks for the European Parliament, mocked Mr Trump's temper and supposed closeness to Russian President Vladimir Putin in a series of tweets. But short of that, he also pledged the USA would raise its own trade barriers to combat unfair trade practices around the world. Trudeau, who threatened retaliatory tariffs, also said Canada would not be "pushed around".
He refused to sign the communiqué, blaming Mr Trudeau for making "false statements" at an end-of-summit news conference, and called the Canadian leader "dishonest & weak".
"If a deal isn't made, that would be a very bad thing for Canada and it would be a very bad thing for Mexico", Trump said.
Trump on Sunday arrived in Singapore, where he and Kim are to meet Tuesday to discuss that nation's nuclear arsenal.
Trump kicked it off yesterday with tweets calling the Prime Minister "dishonest and weak".
Trudeau's office responded to Trump's tweets with a written statement, saying the prime minister's comments in public and in private with Trump were "nothing he hasn't said before" and that he was "focused on everything we accomplished here at the G-7 summit". "$800 billion trade deficit", he said.
In the week leading up to the the G-7 Summit President Trump engaged in the most Trumpian sort of diplomacy: he very publicly attacked out closest allies. We spent two days obtaining a draft and commitments.
At issue are USA tariffs against Canada and Trudeau's effort to retaliate against its neighbor - as well as Trudeau's comment to reporters that all seven leaders had come together to sign a joint declaration after the G-7 meeting. He said that Canada has to stand up for itself.
Josef Braml of the German Council on Foreign Relations said Trump considered diplomacy a waste of time.
French President Emmanuel Macron said "international co-operation can not be dictated by fits of anger and throwaway remarks".
"Let's be serious and worthy of our people", a statement from the French presidency said.
The majority of Canadian exports go to the United States, making Canada uniquely vulnerable to a USA trade war.
But after negotiators for all seven countries crafted a final communiqué that even the reluctant USA delegation agreed to, Trump abruptly lashed out on Twitter from Air Force One on Saturday night.