HANOI, Vietnam (AP) — President Donald Trump is exchanging school yard taunts with North Korea's Kim Jong Un. In a response to North Korea calling Trump's speech in South Korea "reckless remarks by an old lunatic," Trump tweeted from Hanoi on Sunday morning: "Why would Kim Jong-un insult me by calling me 'old,' when I would NEVER call him 'short and fat?'" Trump goes on to say sarcastically, "Oh well, I try so hard to be his friend — and maybe someday that will happen!" Trump has been working to rally global pressure against North Korea's nuclear weapons program on a trip to Asia.