Trump, who is wrapping up a 13-day visit to Asia, tweeted Sunday that North Korean leader Kim Jong-un had insulted him by calling him "old," when he would "never call him 'short and fat.'"

The two men have engaged in an escalating war of words since Pyongyang's July tests of long-range missiles and September detonation of a nuclear weapon that threaten the American mainland.

"We are admired not just for the exercise of our power, but the power of our example," Biden said. "And it matters, the way we conduct our discourse. It matters, the way in which we talk."

The former vice president has recently been reported to be open to running in the 2020 presidential election.  (Yonhap)