But Trump had the last word Friday morning on Twitter when he said "Kim Jong Un of North Korea, who is obviously a madman who doesn't mind starving or killing his people, will be tested like never before!"
North Korea said on Saturday that firing its rockets at the US mainland was "inevitable" after US President Donald Trump called Pyongyang's leader "rocket man", in a further escalation of rhetoric between the two leaders.
About 100,000 people packed Pyongyang's Kim Il Sung Square in the late afternoon in a show of support for Kim's statement vowing to have Trump "pay dearly" for his recent United Nations speech. Such cooperation is critical for Pyongyang, and the most recent sanctions highly increase pressure on the communist country to abandon development of nuclear weapons and long-range missiles.
In addition to the nuclear test, North Korea has launched dozens of missiles since Kim came to power in 2011.
In a tirade against Trump responding to the USA president's thundering speech at the United Nations this week, the North's leader Kim Jong-Un warned of the "highest level of hard-line countermeasure in history".
He added that a collapse of the Iran nuclear deal would give North Korea little incentive to drop its nuclear programme in return for sanctions relief. North Korea's Foreign Minister Ri Yong Ho made the statement about the hydrogen bomb Thursday, according to South Korean media.
The extraordinary statement has raised fears that North Korea could conduct yet another major weapons test in the days ahead.
Yet the speech, which was approximately 500 words when translated to English, refers to Trump multiple times as a "dotard" - an arcane word for an elderly person who is weak minded or senile.
In his state news release, he also stated how his future actions will be beyond "Trump's expectations" and that he'll "tame the mentally deranged U".
Returning insult with insult, Kim said the president was "unfit to hold the prerogative of supreme command of a country".
South Korean TV footage also showed Ri saying he feels "sorry for his aides" when he was asked about Trump's "Rocket man" comments.
"There is a wide range of areas in which Trump has shifted his own positions out of deference to the judgment of the military hierarchy and I don't think that the American military establishment is fund of the idea" of a war with North Korea because it would be "devastating".