GOP presidential front-runner Donald Trump predicted late Thursday that North Korea’s leader is likely a “total nut job.”

“I think it’s a serous problem because he is probably on the wacky side,” he said of Kim Jong Un on Fox News’s “On The Record.”

{mosads}“I mean, you’ve got this mad man playing around with the nukes and it has got to end. He’s certainly — he could be a total nut job, frankly.”

Trump argued that North Korea’s claim that it successfully tested a hydrogen bomb last Wednesday is surprising given its leader’s age.

“It’s amazing for the young guy that [he would] go and take over,” the outspoken billionaire said of Kim, 33.

“You know, you would have thought that those tough generals would’ve said ‘no way this is going to happen’ when the father died,” Trump said, referencing former North Korean leader Kim Jong Il’s death in 2011.

“He’s got to have something going for him because he kept control, which is amazing for a young person to do,” he added of Kim Jong Un, who succeeded his father in December of that year.

Trump then vowed he would pressure China into curbing North Korean aggression should he win the White House in November.

“They don’t live and they don’t breathe without China,” he said of Pyongyang. “They wouldn’t get anything without China.

“China has the power and we have to tell China to straighten out the situation,” Trump continued. “We have power over China because of trade.

“Frankly, if we ever stopped it, believe me – you would see a depression in China like you have never seen a depression before.”

North Korea announced on Wednesday that it had successfully tested its first hydrogen bomb that morning. Pyongyang’s claim startled the global community given the reclusive nation’s unpredictability.

The White House disputed that North Korea now has the most deadly weapon in its arsenal. Analysts said seismic readings of Wednesday’s detonation were not powerful enough for a typical hydrogen bomb’s explosion.

Thermonuclear weapons use a process making them much more powerful than the ones the U.S. utilized against Japan in World War II.