Donald Trump has been involved in a fierce war of words with North Korea in recent months but the pair finally agreed to take part in diplomatic talks.
Talks with North Korea could prevent a war on the Korean peninsula, which Senator Johnson warned could have “devastating” consequences.
Speaking to CNN, Senator Johnson said: “What we need to do is maintain that pressure. We have to recognise the heinous acts committed by Kim Jong-un and again maintain the maximum pressure. It’s that simple.”
Donald Trump insisted a deal with North Korea was “very much in the making” on Friday.
He wrote on Twitter: “The deal with North Korea is very much in the making and will be, if completed, a very good one for the World. Time and place to be determined.”
Senator Johnson said talking is “never a bad idea” but warned Donald Trump must continue to “isolate” the rogue nation through tough economic sanctions.
He added: “I think talking to people is never a bad idea, as long as you maintain that pressure.
“I’ve never quite understood the enormous diplomatic gain by just sitting down and talk to somebody as long as you maintain the pressure so I’d rather talk to people to prevent any kind of miscalculation.
“And let’s face it – a miscalculation on the Korean peninsula could be devastating. So I don’t have a problem in talking to people.”
With their meeting expected to take place before May, the President said: “North Korea has not conducted a missile test since November 28, 2017, and has promised not to do so through our meetings.
“I believe they will honour that commitment!”
At a campaign rally for Republican candidate Rick Saccone in Pennsylvania today, Trump continued his own crusade: “This should have been handled 30 years ago.
“A lot of people thought we were going to war. Now North Korea is saying they want to denuclearise.
“That’s what we do – we handle things.
“Obama would not have done it, neither would Bush, neither would Clinton.”
But the US President was not sure the meeting with Kim Jong-un was inevitable. He said: “Who knows what’s going to happen? It could happen, it couldn’t happen.
”I may leave fast, or we may sit down and make the greatest deal for the world and for all of these countries, including, frankly, North Korea, and that’s what I hope happens.”