WASHINGTON (REUTERS, NEW YORK TIMES) - US President Donald Trump continued his ongoing verbal attacks on Canadian Prime Minister Justin Trudeau on Monday morning (June 11) from Singapore, suggesting that "Justin acts hurt when called out!"

Trump, who is in Singapore for meetings with North Korean leader Kim Jong Un, tweeted that "Fair Trade is now to be called Fool Trade if it is not Reciprocal" and suggested that Canada is "bragging" in an unspecified release about benefiting from US trade.

Mr Trump did not name the document that he was referring to.

"According to a Canada release, they make almost 100 Billion Dollars in Trade with US (guess they were bragging and got caught!). Minimum is 17B. Tax Dairy from us at 270%. Then Justin acts hurt when called out!" he tweeted. US$100 billion is S$133 billion.

"Why should I, as President of the United States, allow countries to continue to make Massive Trade Surpluses, as they have for decades, while our Farmers, Workers & Taxpayers have such a big and unfair price to pay? Not fair to the PEOPLE of America! $800 Billion Trade Deficit..." he tweeted.

On Sunday, a day after Trump refused to sign a communiqué of the Group of Seven major industrial economies, his advisers went on the attack, accusing Prime Minister Trudeau of "betrayal" and a "stab" in the back, even as Canada, Germany and France pushed back against what they called the US president's "insult" and "inconsistency".

The exchange left Trump estranged from America's partners at the moment he is about to stride onto the most important world stage he has assumed since taking office. Aides attributed his outburst over the weekend to his feeling undercut as he prepared to meet Mr Kim, Chairman of North Korea's State Affairs Commission, while critics said he had stiff-armed his friends at the expense of a unified front.

Fair Trade is now to be called Fool Trade if it is not Reciprocal. According to a Canada release, they make almost 100 Billion Dollars in Trade with U.S. (guess they were bragging and got caught!). Minimum is 17B. Tax Dairy from us at 270%. Then Justin acts hurt when called out! — Donald J. Trump (@realDonaldTrump) June 11, 2018

Why should I, as President of the United States, allow countries to continue to make Massive Trade Surpluses, as they have for decades, while our Farmers, Workers & Taxpayers have such a big and unfair price to pay? Not fair to the PEOPLE of America! $800 Billion Trade Deficit... — Donald J. Trump (@realDonaldTrump) June 11, 2018

The latest G-7 meeting, held in Canada on Friday and Saturday, was tense amid disputes over trade, security and other issues.

But after negotiators for all seven countries crafted a final communiqué that even the reluctant US delegation agreed to, Trump abruptly lashed out on Twitter from Air Force One on Saturday night. 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".

By Sunday morning, Trump's aides were adding fire to the attack on Trudeau.

Mr Larry Kudlow, the US President's economic adviser, said Trudeau's comments were "a betrayal" and that he had "stabbed us in the back".

Trump "is not going to let a Canadian prime minister push him around", Kudlow said on CNN's State Of The Union programme, adding, "He is not going to permit any show of weakness on the trip to negotiate with North Korea."

Mr Peter Navarro, the President's trade adviser, was even harsher.

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"There's a special place in hell for any foreign leader that engages in bad-faith diplomacy with President Donald J. Trump and then tries to stab him in the back on the way out the door," Navarro said on Fox News Sunday.

Left unclear was what exactly Mr Trudeau had said that so offended Mr Trump.

During his Saturday news conference, the prime minister was relatively measured but repeated his position that Canada "will not be pushed around" and would respond to US tariffs with tariffs of its own.

Mr Trudeau on Sunday publicly ignored the dispute, instead hailing "the historic and important agreement" that "will help make our economies stronger & people more prosperous", as he wrote on Twitter.

But his Foreign Minister Chrystia Freeland told reporters that if anyone should be insulted, it was Canada, because Mr Trump had cited a national security justification for his tariffs on steel and aluminum.

"The national security pretext is absurd and frankly insulting to Canadians, the closest and strongest ally the United States has had," she said. "That is where the insult lies."

As for the comments by Trump's aides, she said, "Canada does not believe that ad hominem attacks are a particularly appropriate or useful way to conduct our relations with other countries."

Other G-7 members stood with Canada against Trump. "International cooperation can't depend on anger and small words," France's Élysée Palace said in a statement. "Let's be serious and worthy of our people. We spent two days obtaining a draft and commitments. We stick to it. And anyone who leaves and turns their back on them shows their inconsistency."

Prime Minister Theresa May of Britain issued a statement through an aide saying she was "fully supportive of Justin Trudeau".

German Foreign Minister Heiko Maas on Sunday called on European nations to stick together following Trump's announcement.

Negotiators worked late on Friday to craft a statement that all seven leaders could sign.

Trump's delegation objected to the term "rules-based international order" until negotiators compromised by expressing support for "a" rules-based order rather than "the" rules-based order.

In a section on trade, the Americans insisted on using the word "reciprocal", one of Trump's favourite terms. They compromised by expressing support for "creating reciprocal benefits".

They did not refer directly to the Iran nuclear agreement, which Trump just pulled out of, but the Europeans included a reference to the UN Security Council resolution that endorsed the deal. The negotiators included agree-to-disagree language on climate change and on an international commitment to reduce plastics in the world.

And then the statement was released on Saturday night, only to have Trump disavow it.

Mrs May learnt only as her helicopter arrived at the airport for her to board her plane to return to London. "It started out as a good summit because we were actually talking to each other, instead of past each other," said Mr Peter Beyer, the German government's coordinator on trans-Atlantic relations.

But he added, "It looks like the US is no longer a reliable partner in international agreements, and that's bad."

Josef Braml of the German Council on Foreign Relations said Trump considered diplomacy a waste of time.

"He is about to destroy what's left of the liberal world order because he thinks rules and institutions help America's rivals, China and Europe," he said.