Trump mocks North Korea's Kim, says he would never call him 'short and fat'

President Trump said Saturday that he would never call North Korean leader Kim Jong Un “short and fat,” after Kim’s government slammed Trump as an “old lunatic” following a recent speech in neighboring South Korea.

“Why would Kim Jong Un insult me by calling me ‘old’, when I would NEVER call him ‘short and fat?’ Oh well, I try so hard to be his friend -- and maybe someday that will happen!,” Trump tweeted Saturday evening while in Vietnam, as part of his five-nation Asian trip.

Trump was responding to North Korea calling his South Korea speech days earlier: “reckless remarks by an old lunatic."

The president is visiting China, South Korea and other countries in the region in an effort to get them to help put pressure on North Korea to curtail its pursuit of a nuclear weapons arsenal.  Trump said he also spoke while in Vietnam earlier this weekend with Russian President Vladimir Putin about the North Korea issue.

“Do not underestimate us,” Trump said Tuesday in a speech delivered to South Korea's National Assembly. “And do not try us. ... The weapons you're acquiring are not making you safer, they are putting your regime in grave danger. Every step you take down this dark path increases the peril you face."

On Saturday, Kim's government responded by accusing Trump of trying to demonize North Korea, keep it apart from the international community and undermine its government.

"Reckless remarks by an old lunatic like Trump will never scare us or stop our advance," the North's Foreign Ministry said in a statement.

"On the contrary, all this makes us more sure that our choice to promote economic construction at the same time as building up our nuclear force is all the more righteous, and it pushes us to speed up the effort to complete our nuclear force."

North Korea is not known to have tested any of its missiles or nuclear devices since Sept. 15, after a brisk series of tests earlier this year.

The Associated Press contributed to this report.