Trump appeared to reject speculation that meeting had already been discussed quietly before he tweeted.

How people stay informed in the Hermit State of North Korea is always a question, and US President Donald Trump may have answered it Thursday: by Twitter alerts.

Trump said it only took Kim Jong Un 10 minutes to respond to his tweeted proposal for a landmark meeting in June at the border of North and South Korea.

That suggested that someone in Pyongyang -- perhaps Kim himself -- keeps a minute-by-minute watch on what the US tweetmaster-in-chief is saying on social media.

"When I was flying to South Korea I had the idea, you know what, I am going to South Korea, right next to North Korea, right with the border, right near there," Trump told the New Hampshire Today radio program.

"There was no way that anybody knows how to get Kim Jong Un. How do you get him?" Trump said.

"I put out a tweet: 'Hey, I am going to South Korea. If you want to meet for a couple of minutes, let's meet.'"

"And I put it out and he was calling within 10 minutes."

Trump appeared to reject speculation that the meeting had already been discussed quietly before he tweeted on June 29 from the G20 summit in Osaka: "If Chairman Kim of North Korea sees this, I would meet him at the Border/DMZ just to shake his hand and say Hello(?)!"

A little more than a day later, Trump became the first serving US president to step foot in North Korea, where he held brief talks with Kim.

"I mean it's the craziest thing," Trump, an early and now prolific Twitter user, told the radio program.

Twitter, he said, is "an incredible way of communicating for me ... It's a way of getting the word out."

Kim himself has not taken up tweets to communicate his edicts and invitations.

But he appears to be watching.