Left undecided were the order in which those points were to be executed and the definitions of terms like “peace regime” and “complete denuclearization.” After the meeting in Singapore, Mr. Trump declared the question of denuclearization “largely solved,” but the two sides have since been at loggerheads.

Effectively, the countries are locked in the same stalemate they have been in for years. Washington wants North Korea to end its nuclear weapons program. But for the North, those weapons are the only leverage it has to get what it really wants — a formal end to the Korean War and diplomatic recognition from the United States.

The North said as recently as December that it would not dismantle its weapons program until the United States diminished its military capacity in the vicinity of the Korean Peninsula.

Where will the talks take place?

Mr. Trump announced on Friday that the talks would be held in Hanoi, Vietnam’s capital.

Vietnam is a powerful symbolic choice. Like North Korea, Vietnam and the United States had fraught relations for decades after a deadly war. More recently, the countries have normalized relations. Vietnam, like North Korea, is a communist country. Through capitalist reforms it has emerged from international isolation to become one of the world’s fastest-growing economies. It is a model Mr. Trump hopes will inspire North Korea.

Danang, a port city where American soldiers once relaxed on a stretch of sand then known as China Beach, had also been floated as a potential site for the talks. But the North Koreans were reported to prefer Hanoi.

When will the talks occur?

Though a second round of talks had been rumored for months, it was not until Tuesday during Mr. Trump’s State of the Union address that a date was confirmed.

The talks will be held on Feb. 27 and 28, the president said. Mr. Trump was last in Vietnam in November 2017 to attend the Asia-Pacific Economic Cooperation summit meeting.