He made his remarks in an onstage interview at a conference of business executives in Washington organized by The Wall Street Journal. The interviewer, Gerard Baker, an editor at large at The Journal, pressed Mr. Bolton on the logic of holding another summit meeting when North Korea was not making any efforts to denuclearize.

“They’re going to discuss this and look at the commitments that were made in Singapore and have a discussion about how they’re going to accomplish those commitments,” Mr. Bolton said, “and until that happens there’s not going to be any release of the economic sanctions.”

Jean H. Lee, a Korea analyst at the Wilson Center, said the United States would need to prepare carefully before the meeting to have a chance at making progress on those commitments.

“The Trump administration must be just as savvy and just as smart as the North Koreans are in the weeks leading up to the next summit if the goal is to come out of that meeting with concrete progress on denuclearization — and not just a propaganda win for Kim,” she said.

Mr. Bolton has consistently been more critical of North Korea than Mr. Trump or Mike Pompeo, the secretary of state, who has been trying to restart stalled diplomatic efforts.

In August, Mr. Bolton said, “North Korea has not taken the steps we feel are necessary to denuclearize.” That was around the time North Korean officials began emphasizing the need for an end-of-war declaration; the Korean War halted in 1953 with an armistice, and there has been no peace treaty.

President Moon Jae-in of South Korea has agreed with Mr. Kim that such a declaration would be an important step, and South Korean officials have urged their American counterparts to support the move. Mr. Moon has met with Mr. Kim three times this year, in a surprising flurry of diplomacy, and still hopes to host the North Korean leader in Seoul before the end of this year in what would be a historic visit.