- Video report by ITV News Washington Correspondent Robert Moore
US President Donald Trump has described North Korean leader Kim Jong-un as a "rocket man" who is "on a suicide mission for himself' in a speech to the United Nations.
Mr Trump also threatened to "totally destroy" North Korea if the US is forced to defend itself or its allies from aggression by the rogue state.
In a wide-ranging speech at the United Nations General Assembly in New York, Mr Trump also took aim at Iran, labelling an "economically depleted rogue state" whose chief export is violence.
Mr Trump signalled a stronger approach to Tehran, questioning the 2015 nuclear deal with Iran struck by his predecessor Barack Obama.
He said world leaders "cannot abide" by the agreement if it "provides cover" for Iran to eventually build its nuclear programme.
The US administration last week extended sanctions relief to Iran, avoiding imminent action that could implode the landmark agreement.
But the harshest words were saved for North Korea and its 33-year-old dictator.
"Rocket man is on a suicide mission for himself and his regime," Mr Trump said about the North Korean leader.
"If it (the US) is forced to defend itself or its allies, we will have no choice but to totally destroy North Korea."
Mr Trump previously used "Rocket Man" on Twitter on Sunday.
The nickname is an apparent reference to the Sir Elton John song, which Mr Trump sometimes played at campaign rallies.
Mr Trump, who has previously warned of "fire and fury" if Pyongyang does not back down, claimed that "no one has shown more contempt for other nations and for the wellbeing of their own people than the depraved regime in North Korea.".
And he scolded nations that he said have enabled and traded with North Korea, seeming to slight China, though he did not mention it by name.
Mr Trump, who was highly critical of the UN during his election run, stood before world leaders and a global audience and declared that UN members, acting as a collection of self-interested nations, should unite to confront global dangers.
He assured that the United States would not abdicate its leadership position in the world, but said other countries need to contribute more.
It what was the president's first address to the general assembly, Mr Trump also took time to denounce communism and socialism, calling out Venezuela and Cuba.
He said the socialist government had brought a once-thriving nation to the "brink of collapse", and accused its President Nicolas Maduro of stealing power from elected representatives to preserve his "disastrous rule".
"The Venezuelan people are starving and their country is collapsing," he said.
He called that situation "completely unacceptable, and said his administration has imposed tough sanctions on the government and vowed further action.
Mr Trump also put the "corruption and destabilising regime" in Cuba under the spotlight.
He said his administration will not lift sanctions on the communist government until it makes fundamental reforms.