Just days after he boasted about the size of his "nuclear button" in response to North Korea's leader, President Trump said Thursday that he has a "very good relationship" with Kim Jong Un.

"I probably have a very good relationship with Kim Jong Un, " Mr. Trump said in an interview with The Wall Street Journal. "I have relationships with people. I think you people are surprised."

But when asked if he's spoken with Kim, Mr. Trump said, "I don't want to comment on it. I'm not saying I have or haven't. I just don't want to comment."

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On Wednesday, the president said he's willing to consider diplomatic talks with North Korea. According to a readout of a call with South Korea President Moon Jae-In, "President Trump expressed his openness to holding talks between the United States and North Korea at the appropriate time, under the right circumstances."

Mr. Trump called Kim "short and fat" on Twitter in November and has previously called him "rocket man" and a "bad dude" and a "maniac."

Just last week, the president bragged about the size of his "nuclear button" and how it's "much bigger & more powerful" than North Korea's. "North Korean Leader Kim Jong Un just stated that the Nuclear Button is on his desk at all times.' Will someone from his depleted and food starved regime please inform him that I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!" Mr. Trump tweeted.

The president suggested to the Wall Street Journal that his name-calling eventually pays off.

"You'll see that a lot with me," he said about combative tweets, "and then all of the sudden somebody's my best friend. I could give you 20 examples. You could give me 30. I'm a very flexible person."

Meanwhile, former Vice President Joe Biden and Admiral Mike Mullen have said over the last week that they believe the U.S. has never been closer to nuclear war with North Korea.

In an interview with PBS NewsHour's Judy Woodruff, Biden was asked if he agrees with Admiral Mike Mullen's sentiment that the U.S. has never been closer to a nuclear exchange with the rogue state.

"Yeah, I do," Biden said. "And that's why I think that what I worry about -- and I'm worried from the beginning -- is about fundamental miscalculations. This is not a business deal. This is not about who builds the next skyscraper."

"When we engage in activities like 'let's compare the button,' they all -- for different reasons and different motivations -- lose confidence in us," Biden added. "They wonder what the hell we're doing. I'm worried they then decide they're going to try separate ways to figure out how to do this.

In the same interview with the Wall Street Journal, Mr. Trump accused Peter Strzok — the former special counsel agent who exchanged anti-Trump texts with another FBI agent — of "treason."

Strzok's attorney Aitan Goelman called the comment "beyond reckless."

"It is beyond reckless for the President of the United States to accuse Pete Strzok, a man who has devoted his entire adult life to defending this country, of treason," Goelman said in a statement. "It should surprise no one that the president has both the facts and the law wrong."

CBS News' Paula Reid contributed to this report.