John Kelly, Donald Trump's chief-of-staff, appeared to go through an "existential crisis" on Tuesday, social media users joked, as he listened to the president's address to the UN General Assembly.

Mr Trump used his maiden address to the world's leaders to escalate his standoff with North Korea over its nuclear challenge, threatening to "totally destroy" the country of 26 million people and mocking its leader, Kim Jong-un, as a "rocket man."