It's odd, one minute Kim is talking about nuclear war, testing missiles, then he calls Trump "old".
Trump, being the man who he is, took the bait and threw some insults back at North Korean leader Kim Jong-un.
North Korean state-run media outlets have been repeatedly criticizing the president as he tours Asia on a five-nation journey that will take him to Japan, South Korea, China, Vietnam, and the Philippines.
Trump was responding to North Korea calling his South Korea speech days earlier: "reckless remarks by an old lunatic".
In a speech to South Korea's Parliament on Wednesday, Mr Trump warned Pyongyang not to underestimate the U.S., while offering leader Kim Jong Un a better future if he gives up his nuclear ambitions.
On Aug. 8, Trump threatened the regime with "fire and fury like the world has never seen", leading Kim to say he would consider sending missiles into the waters off the coast of Guam in "mid-August". That, according to Pyongyang, only encourages North Korea to "speed up" completing its nuclear armed forces.
North Korea has conducted dozens of ballistic missile tests in defiance of United Nations sanctions.
The morning tweetstorm came as Trump prepared for bilateral meetings with Vietnamese leaders, including a scheduled news conference where he could face more questions about the topics he addressed on Twitter.
"If it did happen it could be a good thing I can tell you for North Korea, but it could also be good for a lot of other places and be good for the rest the world".
North Korea and its nuclear weapons program have plagued the USA for years.
As Trump has made his way through South Korea, Japan and China this week - touting the strength of the USA alliance and commanding North Korea to "not try us" - the regime has remained quiet.
For the last months, the two leaders have been on two ends of a bitter war of words prompted in part by Pyongyang refusal to cease ballistic missile tests and the development of nuclear capabilities.
This isn't the first time Trump and Kim have traded barbs.
He said he asked the Russian leader if he interfered in the 2016 U.S. election and received assurances from Mr Putin that he "absolutely did not meddle".
He said he doesn't know if that friendship will develop, but added it would be "very, very nice if it did".