North Korea's leader Kim Jong-un said his country would consider the "highest level of hard-line countermeasure in history" against the United States in response to Donald Trump's threat to destroy the North.
Calling Trump "mentally deranged" and his comments "the most ferocious declaration of a war in history," Kim said his UN speech on Tuesday confirmed Pyongyang's nuclear program has been "the correct path".
"His remarks ... have convinced me, rather than frightening or stopping me, that the path I chose is correct and that it is the one I have to follow to the last," Mr Kim said in the statement carried by the North's official KCNA news agency, promising to make Mr Trump "pay dearly for his speech".
Mr Trump had warned the North Korean leader in his UN address on Tuesday that the United States, if threatened, would "totally destroy" the country of 26 million people and mocked Kim as a "rocket man" on a suicide mission.
It was the US president's most direct reference to military action so far against the North, which conducted its sixth and largest nuclear test on 3 September.
In addition to the nuclear test, North Korea has launched dozens of missiles since Kim came to power in 2011. Two recent ballistic missiles flew over Japan as Pyongyang advanced toward its goal of creating nuclear warhead-tipped missiles that can hit the US.
In response to Mr Trump's UN speech, North Korea's top diplomat likened the address to "the sound of a barking dog".
The US president signed off on fresh sanctions after trading rhetorical blows with North Korea, authorising the United States treasury to target firms and financial institutions conducting business with the North.
In today's rare direct statement, Mr Kim said the US president would face "results beyond his expectation," without specifying what action North Korea would take next.
"I will surely and definitely tame the mentally deranged US dotard with fire."
He said Mr Trump was "unfit to hold the prerogative of supreme command of a country, and he is surely a rogue and a gangster fond of playing with fire, rather than a politician".
"Now that Trump has denied the existence of and insulted me and my country in front of the eyes of the world.., we will consider with seriousness exercising of a corresponding, highest level of hard-line countermeasure in history," he said.