Trump emerged after a more than hour-long Oval Office meeting with Kim Yong Chol - a general facing U.S. sanctions who is Kim's right-hand man - saying that the summit will go ahead in Singapore on June 12 as originally planned.
"It went very well", President Trump told reporters on the White House lawn.
Washington has said that North Korea's denuclearisation should be a complete and nearly immediate process, while Pyongyang has appeared to put safeguards for the regime's survival as a pre-condition to a process of gradual dismantling, accompanied by a measured lifting of the sanctions. "I have no doubt", the US President said.
This sets Kim apart from his father and grandfather, who were never bold proponents of letter diplomacy and mostly limited the exchange of letters and telegrams with traditional ally Beijing and, to a lesser extent, Moscow.
But on Friday, after meeting with North Korea's Kim Yong-chol, he announced the Sinapore-based talks were back on. "You may be able to see it".
US Secretary of State Mike Pompeo said a North Korean delegation, headed by high-ranking official Kim Yong Chol, with whom he held two days of talks with in NY, would make a rare visit to the White House on Friday and give Trump a letter from Kim.
Trump described the session with Kim Yong Chol as a positive, introductory session.
On the possibility that President Moon Jae-in may also visit Singapore to take part in declaring an end to the Korean War, the official said it could happen if a declaration is made. He wants North Korea to give up its nuclear arms in return for sanctions relief, but the Pyongyang leadership has seen the nuclear program as crucial to its survival and says it can not give it up without security guarantees.
Washington has kept the maximum pressure campaign against the DPRK, including slapping severe economic sanctions on the Asian country.
PRESIDENT DONALD TRUMP: It'll be a beginning.
If the trip comes off - no firm dates have yet been released - he will become the first head of state to meet Kim inside the isolated kingdom. "You're talking about 70 years". "Both parties need to subsequently keep communicating, without this dramatic display in order for this meeting to be meaningful".
The White House did not immediately respond to request for comment Saturday. And he's on the line now.
SCOTT HORSLEY, BYLINE: Good morning. "And I think it's probably going to be a very successful - ultimately, a successful process". And he arrived at the South Portico this afternoon with very little fanfare, actually. This time, Trump did not greet his visitor in person, leaving that task to his chief of staff John Kelly and a top Central Intelligence Agency official.
Mr Kim's letter reportedly expresses his interest in meeting without making any significant concessions or threats in regards to denuclearisation, the Wall Street Journal reports, citing a foreign government official who was briefed on the contents.
But he wound up staying for well over an hour. And just 10 per cent of South Koreans approved of Kim just two months ago. They posed for some pictures there along with Secretary of State Mike Pompeo. Top US officials are often contradicting the US President with national security advisor John Bolton stating that he would like negotiations to be done quickly because a long-term process could wring out concessions from the US, whereas Trump is open to a slower approach. We think it's important.
USA officials now expect the summit to go ahead, but they want North Korea to accept that nuclear disarmament be at the heart of the discussion - and warn that there can be no end to trade sanctions without it. He has undertaken a flurry of diplomatic activity recently, meeting China's president in May, and is expected to attend a summit with Donald Trump this month.
The talks could get contentious.
The summit will still take place on June 12 in the Southeast Asian island nation of Singapore, now only a week and a half away. What has changed? How did we get back to it's game-on June 12?
The visit marks the second time in history a North Korean official has visited the White House. They didn't show up for a preparatory meeting. "We will see what we will see".
The two countries, eyeing the first summit between the USA and the North after six decades of hostility, have also been holding negotiations in Singapore and the demilitarised zone between the two Koreas. "How much? How much?" he said, pointing to reporters as if they were bidders on a not-to-be-missed piece of diplomatic memorabilia.
Pyongyang's envoy joined Pompeo at the apartment of a USA diplomat on Manhattan's East side for talks over an evening meal that lasted about an hour and a half. And they want other things along the line. That's the reason they have the nuclear weapons. He is the most senior North Korean to visit in 18 years, a symbolic sign of easing tensions after fears of war escalated amid North Korean nuclear and missile tests last year. And Trump hinted today at a broader peace agreement. "He will then talk about denuclearization, ending hostility and normalizing relations between the countries".
Kim Jong Un surely knows that he could be held liable for the crimes against humanity of which he and his regime are guilty, and likely suspects that the issue will be raised by the United States if a summit ever occurs. Scott, thanks so much for being with us.
KELLY: That's NPR's Scott Horsley.