President Trump, speaking from Camp David Saturday in the middle of his retreat with key congressional leaders and senior administration officials, said he would “absolutely” engage in phone conversations with North Korean leader Kim Jong Un.

The president made the decision to address reporters about his administration’s 2018 legislative agenda Saturday, but when reporters began asking questions, Mr. Trump veered off message to address North Korea, questions about his mental fitness and the Russia investigation. Hours earlier, faced with criticisms in Michael Wolff’s bombshell book “Fire and Fury: Inside Trump’s White House,” the president took to Twitter from Camp David to defend himself, saying he is “like, really smart” and a very stable genius.

Senior officials in his administration have suggested there must be some preconditions to talks with North Korea. In mid-December, Secretary of State Rex Tillerson said he would be open to speaking with North Korea without preconditions, before backtracking on that statement and insisting North Korea must first reduce the threat of its nuclear weapons program. McMaster in December insisted Tillerson’s initial comment was incorrectly reported.

On Saturday, asked if he would be willing to engage in a phone conversation with the North Korean leader right now, Mr. Trump said, “I always believe in talking.”

“Our stance, you know what it is. We’re very firm,” Mr. Trump continued. “But I would be absolutely, I would do that. No problem with that, at all.”

But the president, asked if that meant no prerequisites to coming to the table, said, “That’s not what I said, at all.”

“Look, right now they’re talking Olympics,” Mr. Trump said of North Korea and South Korea. “It’s a start. It’s a big start. If I weren’t involved they wouldn’t be talking about Olympics right now. They’d be doing no talking or it would be much more serious. He knows I’m not messing around. I’m not messing around. Not even a little bit. Not even 1 percent. He understands that.”