But after a year of mounting tension, diplomacy focused on sport enabled the International Olympic Committee to announce on Saturday that reclusive North Korea will send 22 athletes to the Feb. 9-25 Games.
The Olympics provided a "precious chance to open the door" for talks to resolve the nuclear issue and establish peace on the peninsula, Moon said at the presidential Blue House.
"But no one can be optimistic about how long the current mood for dialogue will last. We need wisdom and efforts to sustain the dialogue opportunities ... beyond the Olympics so that the inter-Korean talks will lead to talks between the United States and North Korea and other forms of dialogue".
While a recent opinion poll showed most South Koreans welcomed the North's participation in the Games, conservative opponents staged a small but noisy rally as a North Korean delegation inspected venues in Seoul for cultural events to be held on the sidelines of the Olympics.
South Korean police intervened when one group of protesters burned a picture of North Korean leader Kim Jong Un on the steps of Seoul's central train station where a delegation from the North had arrived.
Holding a sign saying "We're opposed to Kim Jong Un's Pyongyang Olympics!", the protesters chanted that the North had "snatched" attention for the showpiece event from South Korea.
The North Korean delegation was led by Hyon Song-wol, a popular female singer, who smiled and waved to a crowd at the train station before the protest began.
"Seeing the citizens here welcoming us, I feel we will be able to successfully complete the concert", Hyon was quoted as saying by a Seoul official, according to South Korean media.
Some specific Olympic plans, including marching under a united flag and forming a joint women's ice hockey team, have proven controversial, with conservatives and younger South Koreans upset that an unchastened North Korea is stealing the spotlight.