These WERE our allies...

Now they are tired of trying to explain global economics to a psychopathic toddler.

President Trump upended two days of global economic diplomacy late Saturday, refusing to sign a joint statement with America’s allies, threatening to escalate his trade war on the country’s neighbors and deriding Canada’s prime minister as “very dishonest and weak.”

In a remarkable pair of acrimony-laced tweets from aboard Air Force One as he flew away from the Group of 7 summit toward a meeting with North Korea’s leader, Mr. Trump lashed out at Justin Trudeau. He accused the prime minister, who hosted the seven-nation gathering, of making false statements.

Literally moments after Mr. Trudeau’s government proudly released the joint statement, noting it had been agreed to by all seven countries, Mr. Trump blew apart the veneer of cordiality that had prevailed throughout the two days of meetings in a resort town on the banks of the St. Lawrence River.

“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 as we look at Tariffs on automobiles flooding the U.S. Market!” Mr. Trump wrote.

“PM Justin Trudeau of Canada acted so meek and mild during our @g7 meetings,” Mr. Trump said in a second tweet, “only to give a news conference after I left saying that, ‘US Tariffs were kind of insulting’ and he ‘will not be pushed around.’ Very dishonest & weak. Our Tariffs are in response to his of 270% on dairy!”

Not long after, John Bolton, the president’s national security adviser, tweeted out a dramatic photo of Mr. Trump, arms crossed and scowling, looking defiant as the leaders of the other nations stood in a circle around him.

“Just another #G7 where other countries expect America will always be their bank,” Mr. Bolton wrote as the president’s plane stopped for refueling at Souda Bay on the Greek island of Crete. “The President made it clear today. No more.”

Mr. Trudeau’s office responded to the president’s Twitter barrage with a carefully worded statement.

“We are focused on everything we accomplished here at the summit,” said Cameron Ahmad, a spokesman for Mr. Trudeau. “The prime minister said nothing he hasn’t said before — both in public, and in private conversations with the President.”