United States President Donald Trump on Sunday said North Korean leader Kim Jong-un had “insult[ed] me by calling me ‘old’”, even though he himself would never call him “short and fat”.

Responding to North Korea’s statement on Saturday calling him an “old lunatic”, Trump said he was trying “so hard to be his [Kim’s] friend”, and “maybe someday that will happen”. Trump is on a five-nation visit to Asia, and has stepped up his rhetoric on North Korea in his speeches.

In a series of tweets, Trump also said he hoped to take Russian President Vladimir Putin’s help in solving the “dangerous North Korea crisis”. The tweets came hours after Trump’s meeting with Putin at the Asia-Pacific Economic Cooperation summit in Vietnam.

In a speech in South Korea earlier this week, Trump had warned Pyongyang of “grave danger” if it continued its nuclear weapons programme. North Korea said in response: “Reckless remarks by an old lunatic like Trump will never scare us or stop our advance.”

Trump and Kim have taken jibes at each other in the past few weeks, with Kim once calling Trump a “deranged old man” and “dotard” after being called “Little Rocket Man”.