During a brief meeting on the border between North and South Korea in late June, Mr. Trump and Mr. Kim agreed to resume staff-level negotiations to try to narrow their differences.

But the talks in Stockholm were doomed by the same problem that had bedeviled all previous negotiations between the two countries: deep differences over what the “complete denuclearization” of the peninsula entailed and what concessions they should offer to each other in the first step toward that goal.

In Hanoi, North Korea offered to dismantle a key nuclear fuel-production center, but only if Washington removed the most biting of the international sanctions, such as the ban on its key exports, like coal and textiles. Mr. Trump insisted on a quick and comprehensive elimination of all the North’s nuclear warheads, as well as their means of delivery and production facilities, before easing any of the international sanctions.

Ms. Ortagus, the State Department spokeswoman, said the American negotiators had traveled to Stockholm with “creative ideas and had good discussions” with their North Korean counterparts. Mr. Kim, the chief North Korean negotiator, said his side had explained a “practical” idea on how to end the stalemate, but he accused his American counterparts of repeating their “old position and attitude.”

Kim Dong-yub, a North Korea expert at the Seoul-based Institute for Far Eastern Studies, said, “The negotiations likely have floundered from the beginning because North Korea and the United States both sought to get too much while offering too little.”

On Sunday, the North Korean Foreign Ministry said progress could be made only when the United States ended its policy that “threatens the security of the country and hampers the rights to existence and development of its people.” Mr. Kim, the North Korean negotiator, cited international sanctions and the United States’ joint military exercises with South Korea as part of such policy.

In a speech in April, Kim Jong-un said he would wait until the end of the year for Washington to come up with a more flexible proposal — a deadline his Foreign Ministry reiterated on Sunday. North Korea has since issued vague warnings that it might end a self-imposed moratorium on nuclear and intercontinental ballistic missile tests, which Mr. Trump cited as one of his biggest gains in his on-off diplomacy with the North.