Trump was on board Air Force One on his way to Singapore when he tweeted that the G7 host was "dishonest and weak".
Trump tweeted: "Based on Justin's false statements at his news conference, and the fact that Canada is charging massive Tariffs to our US farmers, workers and companies, I have instructed our US Reps not to endorse the Communique as we look at Tariffs on automobiles flooding the US Market!" He followed up by tweeting: "PM Justin Trudeau of Canada acted so meek and mild during our @G7 meetings 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!"
"His message from Quebec to Singapore is that he is going to meld the industrial democracies to his will - and bring back Russia," said Steve Bannon, Trump's former campaign and White House adviser.
Ever since Trump shocked allies, White House officials, and, by some accounts, the North Koreans themselves when he accepted Kim's March invitation for a meeting, the two leaders have lurched toward an uncertain encounter.
"It's unknown territory in the truest sense, but I really feel confident," Trump told reporters. "I feel that Kim Jong Un wants to do something great for his people and he has that opportunity and he won't have that opportunity again."
Trump's engagement with Kim fulfills the North Korean ruling family's long-unrequited yearning for international legitimacy, itself a substantial concession that could weaken more than a generation of US efforts to isolate the country on the global stage.
A triumvirate of forces is bringing the meeting to fruition, said Scott Snyder of the Council on Foreign Relations, describing the summit as "Produced by Kim, directed by (South Korean President Moon Jae In), and inspired by Trump."
The hard-hitting sanctions and desire for legitimacy brought the youthful Kim to the table. The South Korean leader's efforts to avert a potentially catastrophic US first strike pushed both leaders to take a risk. And Trump is the first US president willing to sit-down with the autocratic ruler with so few concessions, believing his self-professed negotiating prowess will guide him though uncharted diplomatic waters.
Trump said the outcome will rely heavily on his own instincts. He said he will know "within the first minute" of meeting Kim whether the North Korean leader is serious about the nuclear negotiations. "Within the first minute, I'll know. My touch, my feel - that's what I do," he said.
"I think I'll know pretty quickly whether or not, in my opinion, something positive will happen. And if I think it won't happen, I'm not going to waste my time. I don't want to waste his time."
- AP
