'Kim Jong-un called me 'old', I will never call him 'short and fat', says Trump

Trump made the comment after attending the Asia-Pacific Economic Cooperation (APEC) summit in Vietnam. In a series of tweets, he also said the Chinese President was "upping sanctions" on North Korea in response to its nuclear and missile programs and that Xi Jinping wanted Pyongyang to "denuclearize".

During Trump's visit to Beijing last week, Xi reiterated that China would strive for the denuclearisation of the Korean peninsula but offered no hint that it would change tack on North Korea, with which it fought side by side in the 1950-53 Korean war against US-led forces.

"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.

Trump has traded insults and threats with Kim in the past amid escalating tensions over Pyongyang's nuclear and missile programs as North Korea races towards its goal of developing a nuclear-tipped missile capable of reaching the US – something Trump has vowed to prevent.

North Korea conducted its sixth and most powerful nuclear bomb test on September 3, prompting another round of UN sanctions. In September, Kim described Trump as a "mentally deranged US dotard" whom he would tame with fire. His comments came after Trump asserted in his maiden United Nations address to "totally destroy" the country of 26 million people if the United States were threatened.

After North Korea's Foreign Minister Ri Yong Ho addressed the UN General Assembly in September, Trump tweeted: "Just heard Foreign Minister of North Korea speak at UN. If he echoes thoughts of Little Rocket Man, they won't be around much longer!" North Korea has conducted dozens of ballistic missile tests in defiance of UN sanctions. The North has vowed to never give up its weapons programmes.