President trump comes to make peace with one of America's fiercest enemies. Just as he takes aim at a key U.S. Ally tonight. The president comes straight from a tense meeting wh America's staunchest allies. This remarkable photo. So many studying the body language after the president refused to step down from the tariffs he's going to impose on allies, including Canada. The administration crossest criticism is for Canada's prime minister Justin Trudeau who said his country won't be pushed around. ABC's chief global affairs correspondent Martha Raddatz with the war of words unfolding elsewhere. Reporter: Tonight, president trump and his top economic advisors attacking one of America's closest allies accusing Canadian prime minister Justin Trudeau of undermining the peace talks with Kim Jong-un. He really kind of stabbed us in the back. Reporter: It comes just hours after the president left the g-7 summit, where he frustrated world leaders by refusing to back away from his plans to impose stiff tariffs on aluminum and steel from Canada and other allies. He called it a matter of national security. Trudeau called that insulting, and vowed to retaliate by slapping tariffs on American goods. It is not something we relish doing, but it's something we absolutely will do. Canadians, we're polite and 're reasonable, but we also won't be pushed around. Reporter: Trump was furious, in an angry tweet calling Trudeau "Very dishonest and weak." And then a stunning decision, the American president refused to sign the traditional statement of solidarity with the g-7 allies, a statement his own team hped draft. Today, the message from the white house: Blame Canada. 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. Reporter: The president's top economic advisor called Trudeau's words a betrayal. A sophomoric political stunt and a slap in the face. POTUS is not going to let a Canadian prime minister push him around, he is not going to permit any show of weakness on the trip to negotiate with north Korea, Kim must not see American weakness. Reporter: That wasn't all. He ought to come out and apologize and in the name of the western allies, okay? He ought to come out today and wish president trump well in the negotiations. Reporter: So now as he heads into talks with one of America's greatest enemies, president trump's relations with America's closest friends now plunging to a new low. From French president Emanuel macron today a warning, "International cooperation cannot depend on fits of anger." This is something to witness today. Martha Raddatz with us in Singapore as well. To think the president is going to be sitting down with Kim Jong-un and this war of words with some of our closest allies. Larry kudlow seemed to indicate this harsh attack is because the summit is happening right after the g-7. Which is inexplicable. What Trudeau was doing was defending his country which you heard trump do over and over again. He's the one that started this with the tariffs. It was also Donald Trump who turned to name calling. What the connection with the summit is is unclear. Seems the white house knows the world is watching everythi. Martha Raddatz within Singapore. We hope you'll stay with ABC news for full coverage of this summit. Full coverage right here on ABC news. "Gma" first thing in the morning live when president trump an Kim Jong-un meet for the first time. I'll be joining George, Martha, Jon and the entire team. When president trump and Kim Jong-un meet for the first time. We'll be live.