Transcript for Trump: 'Severe consequences' if Iran starts its nuclear program again

North Korea are on their way home right now. President trump first tweeting that they were on their way. The three men flying out with secretary of state Mike Pompeo. President trump says he plans to be there when they arrive at Andrews air force base at 2:00 in the morning. Just as Iran tonight sends the president its own message, after he tore up the nuclear deal. ABC's chief white house correspondent Jonathan Karl leading us off. Reporter: The president made the announcement himself, calling the release of the American prisoners an important moment for the country. Right now, flying back are three, what they were calling hostages, we call them fine people. Three really fine people. Seem to be healthy, they will be landing at 2:00 in the morning at Andrews air force base, and I'll be there to greet them. Reporter: Secretary of state Mike Pompeo traveled to North Korea to secure their release, meeting for a second time with Kim Jong-un. The three former prisoners are korean-american. Two of them detained last year, the third imprisoned since 2015. And I appreciate Kim Jong-un doing this and allowing them to go. Reporter: The president now focused on meeting Kim himself. Mr. President, where is the summit going to take place? We're going to announce that in three days. Within three days. Reporter: Will it be the dmz? It will not be there. Reporter: The location still a mystery. Kim seldom travels. Though North Korea today released this picture of the north Korean dictator on his plane in China. The president is already envisioning making history. Do you deserve the Nobel prize, do you think? Everyone thinks so, but I would never say it. You know what I want to do? I want to get it finished. The prize I want is victory for the world. Reporter: But even as he pursues one nuclear deal, he is facing global blowback for pulling out of another. In Iran today, anti-american protests, including the burning of American flags and photos of president trump. Lawmakers there questioning the president's, quote, mental capacity, and threatening to restate its nuclear program. What are you going to do if Iran starts up their nuclear program again? Iran will find out. If they do, there will be very severe consequence. Let's get to Jon Karl at the white house tonight. Iran had agreed to nuclear inspections. As we know, that wasn't enough to keep president trump in the agreement. North Korea already has nuclear weapons. Will Kim Jong-un agree to inspections anywhere close to what Iran was already allowing? Reporter: That's uncertain, David. North Korea has cut itself off from almost all of the outside world for more than a half a century. It is hard to imagine that such an isolated and secretive regime would suddenly open itself up, including its most sensitive military facilities, but the white house insists that any deal with North Korea will be fully verifiable, and that would inspections beyond anything we have ever seen in North Korea. All right, all of this as we await the arrival of the three Americans. Jon Karl, thank you.

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