Bong Young-shik, a research fellow at Yonsei University's Institute for North Korean Studies in Seoul, said time will tell whether the meeting - which might have been unknown in Washington - could affect South Korea's standing as a close ally with the United States.
Unlike the previous summit in April, which had been planned in advance and included ceremonial elements and press facilities for some 3,000 journalists from across the world, today's summit took place with no forewarning.
So what does the cancellation of the Trump-Kim summit in Singapore mean for the region?
But the official could also have been en route to Singapore to prepare for the US-North Korea summit, and possibly his plan changed after Trump cancelled the meeting.
He also vowed to "create conditions for dialogue with North Korea", State Department spokeswoman Heather Nauert said.
Analysts say Kim's diplomatic outreach in recent months after a flurry of nuclear and missile tests in 2017 indicates he is eager for sanctions relief to build his economy and the worldwide legitimacy the summit with Trump would provide.
Moon's office said that during their two-hour meeting, the two leaders also discussed carrying out the peace commitments they agreed to at their first summit, held at Panmunjom on April 27, but didn't elaborate.
Trump, speaking Friday to graduates at the U.S. Naval Academy, did not mention North Korea directly, but he stressed the United States' military might.
The breaking point appeared to be comments by a senior North Korean official criticizing Vice President Mike Pence last week.
But North Korean state media, in a measured response, stated that they were still open to meeting the USA president.
For the North, that was a deeply provocative comparison for two reasons. Libya gave up its nuclear program at an early stage only to see its longtime dictator overthrown and brutally killed years later. "If North Korea is serious, then we look forward to hearing from them at the highest levels".
North Korea is looking at a different type of deal.
But he left the door open to future meetings and Pyongyang's immediate reaction was to say it was willing to sit down "at any time", prompting Trump to reply that the Singapore summit could still take place. The North has spent decades building a nuclear and missile capability to deter the US, and Aum remains skeptical that it's truly interested in giving up those weapons although it sees value in going down that path to see what benefits it might get.
But the latest developments also exemplified how quickly aspirations for successful talks between North Korea and the US - which remain technically at war - can rise and fall. He said Kim would get security guarantees if he denuclearizes.
For the second time in a month, South and North Korea leaders make sure the historic meeting between North Korea leader Kim Jong Un and the U.S.
He said, if the summit does happen it will likely remain in Singapore and be on that same June 12 date.
When the two met in Beijing in March, Xi accepted Kim's invitation to visit Pyongyang as soon as possible.
Earlier, the U.S. allies in Asia were blindsided by Trump's cancellation.
- Chelsea have learnt from last year's FA Cup final, insists Cesc Fabregas
- Statistically Speaking: Vasilevskiy steals one for the Lightning
- Starting Aron Baynes proves to be ‘right decision’ for Boston Celtics
- LeBron James dissects Chris Paul's Game 5 performance
- How The EU's New GDPR Law Gives People More Power Online (HBO)
- 7 stats explaining how the Cavaliers won Game 6
- Boston Celtics: How to watch, listen and more
- Remembering the vets on Memorial Day
- Ricciardo fastest as Verstappen crashes in FP3
- So Pusha T's 'brilliant' album now means we've forgiven Kanye?