The head of the group that won the Nobel Peace Prize called Trump a 'moron' - and had a pointed message for him and Kim Jong Un

Two days before her organization became the world's newest Nobel Peace Prize winner, Beatrice Fihn took a shot at the man behind one of the largest nuclear weapons stockpiles - US President Donald Trump.

In a tweet earlier this week, Fihn, the executive director of the International Campaign to Abolish Nuclear Weapons (ICAN), made a blunt assessment of the president, writing, "Donald Trump is a moron."

She elaborated Friday that she was responding to recent media reports that Secretary of State Rex Tillerson used the same word to describe Trump this summer, telling Reuters she intended it as a joke, "which I kind of regret now."

However, Fihn added, "I think that the election of President Donald Trump has made a lot of people very uncomfortable with the fact that he alone can authorize the use of nuclear weapons."

Fihn, whose group is behind the first treaty to prohibit nuclear weapons, said that Trump's impulsive character illustrated the importance of banning them.

"A man you can bait with a tweet seems to be taking irrational decisions very quickly and not listening to expertise, it just puts a spotlight on what do nuclear weapons really mean," she said. "There are no right hands for the wrong weapons."

Asked by Reuters if she had a message for Trump and Kim Jong Un, the North Korean leader whose nuclear efforts have publicly enraged the US president, Fihn said, "they need to stop."

"Nuclear weapons are illegal. Threatening to use nuclear weapons is illegal. Having nuclear weapons, possessing nuclear weapons, developing nuclear weapons, is illegal, and they need to stop," she said.

Here's the tweet where Fihn calls Trump a "moron":