“Our leaders have impact on attitudes. And I just think it’s a big mistake and it’s beneath the office,” he added.
Biden’s remarks came a day after Trump exchanged school yard taunts with the North Korean leader. In fact, the former VP was specifically asked to provide his views on the president’s tweet over the weekend, in which Trump called Kim "short and fat.”
“Why would Kim Jong-un insult me by calling me ‘old,’ when I would NEVER call him ‘short and fat?’” Trump tweeted on Sunday. “Oh well, I try so hard to be his friend - and maybe someday that will happen!”
“I just think in a context of just — sort of — common decency,” Biden told NBC.
“I mean, it’s not the way, you know — when your children hear a president referring to anybody that way, I mean our children are listening. I mean, these things matter,” he added.
Last week, the North Korean Foreign Ministry said in a statement that “no-one can predict when the lunatic old man of the White House, lost to sense, will start a nuclear war," referring to Trump's war rhetoric against North Korea.
Trump has taken an increasingly hostile stance toward Pyongyang over its nuclear weapons and ballistic missile tests. In a speech to the UN General Assembly in September, the US president threatened to “totally destroy” North Korea if necessary.
In return, Kim called Trump a "mentally deranged dotard" and threatened to "tame him with fire."
Trump has often deviated from diplomatic protocols and attacked leaders of other nations by calling them names.
He has derided the North Korean leader as a “rocket man,” a move that experts said was unbecoming of a president.