But, speaking to CBS, Mr Trump said that Mr Kim must be a "pretty smart cookie" to keep hold of power in his country.
“People are saying, 'Is he sane?' I have no idea.... but he was a young man of 26 or 27... when his father died. He's dealing with obviously very tough people, in particular the generals and others.
”And at a very young age, he was able to assume power. A lot of people, I'm sure, tried to take that power away, whether it was his uncle or anybody else. And he was able to do it. So obviously, he's a pretty smart cookie,“ Mr Trump said.
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