North Korea, South Korea agree to end war, denuclearize the peninsula

The nations signed an armistice when the fighting ended in 1953, but have now agreed to pursue a proper peace agreement.
7:06 | 04/28/18

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Transcript for North Korea, South Korea agree to end war, denuclearize the peninsula
?????? an unprecedented moment between leaders of two nations still technically at war. Breaking news overseas. Reporter: Surrounded by a swarm of bodyguards, the usually secretive Kim Jong-un emerging from the northern side of the dmz. Wearing his trademark Mao suit, Kim walks over, smiling, to the cease-fire line separating north and South Korea. For this handshake with south Korean president moon jae-in. A remarkable summit viewed live around the globe. Reporter: Kim Jong-un simply stepping over the most heavily fortified border in the world. You feel the weight of history when you walk or put your toe on that other line. Reporter: Then president moon says, you've come to the south, when can I come to the north? And Kim Jong-un says, why don't you try now? Oh, they're holding hands. He went back into the north, look at that, almost as if they're erasing the line. Reporter: A ceremonial honor guard noting 5,000 years of shared Korean culture. But there was also laughter. Kim Jong-un turning his nuclear tests into a punch line. "I won't interrupt your sleep anymore with early morning missile tests," he said. The two men so different seemed to enjoy it all, chatting among the trees, on a picnic bench alone, for almost 45 minutes. Introducing their wives, Kim Jong-un's wife all smiles. The two leaders promising to sign a peace treaty this year formally ending the Korean war, pledging the denuclearization of the peninsula. Arms raised in triumph. Then an awkward embrace. Afterwards Kim Jong-un stepping out onto the world stage as a statesman for the first time. Saying, we are one nation and cannot be separated, we are one blood. With that promise of peace, North Korea also agreeing to diplomatic talks with the U.S. It will be the first time any sitting U.S. President will meet with a north Korean leader. Things have changed very radically from a few months ago. You know the name-calling and a lot of other things. They're treating us with great respect. Reporter: It's an astonishing turn of events. Just this past July, North Korea tested an intercontinental ballistic missile, going higher and farther than ever before. Kim Jong-un called it a fourth of July gift to the trump administration. North Korea best not make any more threats to the united States. They will be met with fire and fury like the world has never seen. Reporter: The U.S. Intelligence analysts believed North Korea had produced a nuclear warhead with the capability of reaching the U.S. Mainland. We will have no choice but to totally destroy North Korea. Rocket man is on a suicide mission for himself and for his regime. Reporter: When we visited the port city of pusan, we noticed president trump's heated rhetoric had everyday Koreans on edge. Robert Kelly teaches politics here in pusan, talking about the risks of nuclear armageddon. So the idea is that, I'm holding a gun to your head, you're holding a gun to my head, as long as we both don't pull the trigger, we're both okay. That's classic arms control, brinksmanship. Yeah, it's nuclear deterrence. Reporter: A delicate balance of power with neighboring countries like China too. ABC's Bob woodruff traveled over 800 miles along the border. This farm barrier right here, that is North Korea. Are you afraid of these nuclear bombs that Kim Jong-un is developing? Yeah, very dangerous. You're worried about it. Yeah, very dangerous. Yeah, yeah. What do you think we can do about it? Can we stop him from doing this? Peaceful solution. Peaceful solution. Reporter: But this year a pathway to peace opened up at the winter olympics in pyeongchang with the newly elected south Korean leader, the two Koreas agreeing to field a joint women's hockey team for the winter olympics. And the president who once said negotiating with North Korea was a waste of time accepts the offer. The speed of this is quite extraordinary. And people are especially concerned. Because Donald Trump would pushback. He's unlike anybody else who's ever dealt with a north Korean leader. Maybe in the end that's what brought them together. Reporter: It will be a delicate truce if history is any guide, trusting the north Korean regime can be a risky proposition. Even if president trump sits down and the north Koreans promise to denuclearize, we are a long, long way from knowing whether they will actually do that. Reporter: Kim Jong-un stands accused of starving his own people, brutally executing and torturing members of his own family and inner circle for disagreeing with his policies. It's a gulag. There's massive human rights violations. People are starving. There's a whole effort that needs to happen. You really have to remember what's going on inside that country and what he's been responsible for. I cannot look at him without thinking of Otto Warmbier. Reporter: 22-year-old American Otto Warmbier was detained in North Korea in 2016, accused of stealing a propaganda poster and sentenced to 15 years' hard labor. Please save my life, please think of my family. Reporter: The north Koreans returned him to the U.S. In June of last year after Warmbier suffered a brain injury and fell into a coma. Their son, who was just returned from North Korea with severe brain damage, has now died. Reporter: North Korean officials denied cruelty saying, we provided him with medical treatment and care with all sincerity on a humanitarian basis until his return to the U.S." Yesterday Warmbier's parents filed a lawsuit against the government of North Korea alleging their son was brutally tortured and murdered by Kim Jong-un's criminal regime during 17 months of captivity. It's a brutal regime. And we'll be able to handle it. Reporter: Perhaps prematurely, many have credited president trump with ending this nuclear standoff. There's even talk of a Nobel peace prize. I think the responsibility has fallen on the shoulders of the president of the united States. And I think we have -- I think I have a responsibility to see if I can do it. President trump was handed the worst cards in the north Korean situation of any president before him. All the presidents before him who were negotiating did not have a North Korea that was capable or very close to being capable of launching a missile with a nuclear warhead. Reporter: It's been more than 60 years since the cease-fire in a war that cost hundreds of thousands of lives on both sides. It's unclear if this truce will pass the test of time.

This transcript has been automatically generated and may not be 100% accurate.

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