Speaking on Friday in Vietnam, Trump again criticised North Korea's "twisted fantasies of violent conquest and nuclear blackmail".
He has tried to rally support to curb Pyongyang's rogue weapons programme during his trip, urging regional powers to stand united against North Korea.
While North Korea has launched around two dozen missiles this year, including an intercontinental ballistic missile that can strike parts, if not most, of the continental US, and tested a staged thermonuclear weapon with an explosive yield far greater than anything the regime has previously tested, the North has not engaged in major provocations in almost two months.
With tensions running high over North Korea, Trump mocked his nemesis Kim, deviously calling him "short and fat", after Pyongyang's spokesman dubbed Trump a "dotard".
North Korea is extremely sensitive to any remarks, even if not meant seriously that it sees as disrespectful of the country' ruling Kim dynasty, whose members are revered as near deities.
In the meantime, the 25 million inhabitants of the South Korean capital, Seoul would be in grave danger from the enemy to the north and that United States and allied forces would be "subject to attack by conventional or chemical weapons" which would further delay their entry into the war.
U.S. president Donald Trump took his verbal jousting with Kim Jong-un to a new level on Sunday, taunting the North Korean leader over his height and weight before musing over the idea of them eventually becoming friends.
"Unusual things happen in life", Trump said. "I don't know that it will, but it would be very, very nice if it did", he said. "All we seek really is peace".
Asked by a reporter if the subject of Russian election interference came up, Trump said: "He said he absolutely did not meddle in our election". The US leader seemed to suggest that buying what he called the "greatest missiles in the world" would help wipe out a trade imbalance.
Kelly said the White House staff prepared Trump for the trip in more traditional ways: "We did the staff work, got him ready to go, and then at each place we brief him up on whatever the next event is and all that", he said.
He said he asked the Russian leader if he interfered in the 2016 U.S. election and received assurances from Mr Putin that he "absolutely did not meddle".
Mr Duterte took steps to thaw frosty relations with China after he won the presidency previous year.