When you know, you know.

That’s how President Donald Trump feels about whether it’s worth pursuing a relationship with Kim Jong Un, going by remarks at a press conference Saturday.

The U.S. leader was rushing to catch a flight to meet his North Korean counterpart, having bailed early on his old gang of friends, the Group of Seven, who were holding a summit in Quebec.

At the unprecedented talks in Singapore, “The Art of the Deal” author Trump hopes to get Kim to agree to denuclearize — that is, to abandon North Korea’s nuclear weapons program.

Asked how long it would take for him to figure out whether Kim is serious about giving it up, Trump jumps in to answer: “I think within the first minute.”

“How?” the reporter asks.

“Just my touch, my feel,” the president says. “That’s what I do.”

Officials from Washington and Pyongyang have been in heated horse-trading for the high-stakes summit since April, when North Korea first hinted it would be open to discussing denuclearization.

Whether those nuclear vows are heartfelt has been a worry for the White House. Trump will walk away from the negotiating table rather than be “played” by North Korea with false promises, Vice President Mike Pence has said.

Maybe that’s why Trump has been telling reporters this week that he didn’t feel he had to prepare much for the historic get-together. “It’s about the attitude,” he said.

A game theorist breaks down how the Trump-Kim talks will play out

After hitting some bumps, the on-again off-again meeting between Trump and Kim is scheduled for Tuesday at 9 a.m. Singapore time, or 9 p.m. on Monday Eastern Time. If it ends in a nuclear deal, many months of getting the fine print down will follow.

Right now, the Trump-Kim face-to-face seems fairly certain to happen — though it could be a short one, if the U.S. leader doesn’t like the vibe.

“You know they say you know if you like somebody in the first five seconds? ... I think that very quickly I’ll know whether or not something good is going to happen,” Trump said in the Quebec presser.

“I also think I’ll know whether or not it will happen fast ... it may not.”

Check out: Kim got ‘on his hands and knees and begged’ for summit, says Rudy Giuliani