Transcript for Trump clashes with America's G-7 allies

Want to bring in our chief white house correspondent Jon Karl. You're across town with the white house delegation. We heard from secretary of state Mike Pompeo and he made it very clear that they've been hammering out the details of how this is going to go with the north Koreans right up until the last minute. Reporter: He called this a mission of peace, George, and said he's optimistic, said they're making progress more quickly than he anticipated. But it's quite clear that the best case scenario from the white house view here is that there will be a general commitment on denuclearization with the details to be worked out later so, George, the clearest measure of whether or not this has been successful is if there is another meeting, another meeting between Kim Jong-un and Donald Trump put in place after this summit is over. Also taking pains to show how much president trump has prepared for this meeting. Reporter: No doubt. I talked about how the president's been preparing for this. Also talked about the extensive amount of experts that have been part of this process, dozens of ph.d.s, experts in nuclearization who could look at the technical details of an agreement if one is reached, the verification process. This is not just Donald Trump winging it although this first meeting will be a one-on-one meeting just Donald Trump, Kim Jong-un and their translators. Yeah, they're not going to bring in the full delegation until after that. We're seeing extraordinary diplomacy even as the president is reaching out to one of America's sworn enemies for almost 70 year, it's coming off this g7 summit where he's had such harsh criticism for our closest allies. That tweet storm about the Canadian prime minister Justin Trudeau backed up by the president's staff, as well. Reporter: It's something -- I haven't heard a president, a white house talk about a leader the way this white house has talked about Justin Trudeau since George Bush was talking about Saddam hussein. One of the president's top advisers suggested there is a special place in hell for the Canadian prime minister. They're trying to portray this as an effort by the president to show toughness coming into this meeting, that he won't be pushed around but, George, I don't know if anybody could have anticipated we'd be in a situation where the white house, where the president is talking more harshly about the Canadian prime minister than about the dictator of North Korea. No, it's really something although secretary of state Mike Pompeo said he's unconcerned, said the allies are still united. We'll come back to you later.

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