Transcript for Future challenges remain to verify agreements with North Korea
I'm David Muir live from Singapore. We continue our special edition of "Nightline." And I want to bring inur chief white house correspondent jonaan Karl, this historic moment, this letter signed by president trump and Kim Jong un a short time ago. And we heard the president tell George Stephanopoulos in the first paragraph, now we've seen it. They've both committed to security guarantees to north Korea but airm and unwavering commitment to complete denuclearization of the Korean peninsula. Repter: David I have to say reading that agreeme and hearing what the president told George I is becoming increasingly clearhat Kim Jong un got a lot out of thisummit. There were signifint concessions made by president trump in this process. You mentioned the security guarantees, ao what told George about suspending joint military exercises with the south Koreans. That's a major issue for the north Koreans, around the president is willing do away those joint military exercises, and even on that commitment from chrman Kim, from Kim Jong un, to complete declearization of the Korean peninsula. That's phrase. Words are really important here. Complete denuclearization of the Korean peninsula. It doesn't include a mantra for the unid states, that what we needed was complete, verifiable, irreversible, denuclearization. Each one of those words is important. And in that, in that joint communique, you only see the word complete. How's itoing be verified? Will there be steps made to make sure it is irreversible. That the north couldn'timply reconstitute their nuclear program after gettinghatever rewards they would get. So I see significant concessions here by presidentrump, and it's not exactly clear what the United States has gotten in return. All right, John Karl right ere at the Capella hotel on sentosa island. The president is going to take questions from the international press corps here and when he does,e will break back in live with that. But in the meantime I want to go to Martha Raddatz. You heard George prose the -- ess the president on that. How do you verify. Presint trump made that clear, they Wil have to have denuclearization, but as John pointed out. Verifiable. Irreversible. They can get data from the very beginning, but this is going to be a very long process, whatever happened today, whatever concessions were made, they're going to have T follow up with that and verify. Thank you. And as you heard the president tell George there in that interview, that he did in fact trust Kim Jong un during H several hours with him day, that face-tce, and that meeting THA grew. They both had their national security advisers in the room. He said I trustim at least for now. We'll have much more on the news breaking right here in Singapore in a moment.
This transcript has been automatically generated and may not be 100% accurate.