Transcript for North Korea makes new threat as Trump arrives in South Korea
Reporter: Not long ago the president called talking to North Korea a waste of time, not anymore. I really believe that it makes sense for North Korea to come to the table and to make a deal that's good F the people of North Korea and the people of the world. Reporter: He's not ruling out military action but the president is acknowledging the steep cost of war on the Korean peninsula. We sent three of the largest aircraft carriers world and they're right now positioned and have a nuclear submarine also positioned. We have many things happening that we hope, we hope do not go further. We hope to god we never have to use. Reporter: Meeting with south Korea's president 35 from the north Korean border the president ditched the bellicose rhetoric about North Korea. No more taunting of rocket man Kim Jong-un, no talk of fire and fury. Instead, hope for diplomatic progress. I do see certain movement, yes, but let's see what happens. Reporter: In his first visit here as president, he was welcomed by South Korea's president moon who took office earlier this year urging a less confrontational approach to dealing with Kim Jong-un. The president's newly diplomatic and hopeful tone was also on display at camp Humphries, a joint U.S. South Korean military outpost not far from the border with North Korea. Ultimately it'll all work out because it always works out. Has to work out. Reporter: Even as the president talked up diplomacy, he seemed to surprise south Korea's president by saying that South Korea would soon be buying billions of dollars in U.S. Made weapons. There were no arm sales that were announced but the president predicted that they would come and they would bring lots of American jobs. Robin. We'll see. All right, Jon, thank you.
This transcript has been automatically generated and may not be 100% accurate.