But questions remained about whether the United States gave up more than it gained what had been a much-anticipated meeting between Mr. Trump and Mr. Kim.

North Korea state media reported on Wednesday that Mr. Kim won major concessions from the American president, including an agreement by Mr. Trump to a phased, “step-by-step” denuclearization process for the North, rather than the immediate dismantling of its nuclear capability.

American hard-liners like John R. Bolton, now Mr. Trump’s national security adviser, have opposed that approach. In the past, Mr. Bolton had argued that the North must quickly dismantle and ship out its nuclear weapons program in its entirety, as Libya did more than a decade ago.

The official Korean Central News Agency also reported that Mr. Trump promised to eventually lift sanctions against the North and cease military exercises with South Korea.