Moon has expressed his intention to use the Winter Olympics as a chance to make diplomatic inroads with the North and restore normalized communications, following months of high tensions on the Peninsula.
In a stark illustration of his efforts to pull in Pyongyang without pushing away Washington, Moon watched short-track speedskating with Vice President Mike Pence at the Pyeongchang Winter Olympics on Saturday night, February 10.
It would be the first summit between the leaders of the two Koreas in more than a decade.
Joseph DeTrani, former US special envoy for nuclear talks with North Korea, said Moon should make it clear to Kim that he wants to discuss the nuclear and missile issues at the summit.
Throughout the ceremony there were constant winks to peace, such as the theme "Imagine" by John Lennon, an ode to coexistence, sung by four well-known South Korean singers.
Switzerland's Alina Muller nearly single-handedly spoiled Korea's Olympic unity moment on Saturday, scoring four goals to power the Swiss to an 8-0 win over Korea's unified women's ice hockey team.
But South Korea's presidential Blue House said Pence had a meeting scheduled with United States athletes and had only planned to stay briefly to greet other officials.
So, President Moon (if you are reading this) allow me to say: "Be on your guard, sir!"
United States Vice-President Mike Pence was also present and led the USA delegation.
US officials have been urging South Korea to be cautious in its rapprochement with the North - a point Pence drilled home in private meetings with Moon on Thursday. They stressed the North Koreans in the VIP box had watched Pence, Moon and Abe hold a running discussion in the front row for the more than two-hour ceremonies.
Saturday's meeting also involved the North's ceremonial head of state, Kim Yong-nam, who led what apparently turned out to be a 21-member delegation to the opening ceremony of the PyeongChang Olympics on Friday.
Pence and Moon were expected to view men's short-track speedskating together prior to the women's event, as an American and a Korean were competing against each other, but Moon kept Pence waiting and missed the event entirely.
Officials traveling with Pence said it would be fair to characterize his failure to interact with the North Koreans as a mutual decision, with neither side making any public overtures. "Moon should be aware that he has to urge denuclearisation to North Korea by himself, not depending on dialogue between the USA and North Korea", an editorial in the Yomiuri Newspaper read. Kim Yo Jong is 28 years old, according to the US government.
Kim Yo Jong offered an invitation from her brother for Moon to visit the North, in the strongest sign yet of an expanding diplomatic opening opposed by the U.S. He left the reception five minutes later.
Japanese Prime Minister Shinzo Abe has warned South Korean President Moon Jae-in not to fall for North Korea's "smile diplomacy" during the Olympics, saying the North remains committed to developing nuclear weapons and missiles even while pursuing talks with the South.
Kim's sister is said to be acting as his special envoy in the south during the Games.
By also sending a youthful, photogenic individual who would surely draw global attention at the Olympics, Kim might have also been trying to construct a fresher image of the country, particularly in face of USA efforts to use the Olympics as an occasion to highlight the North's brutal human rights record.
North Korea conducted its largest nuclear test a year ago and said it had developed a missile capable of carrying a warhead to the United States.
White House officials and other critics believe North Korea is trying to use the global stage to gain sympathy and ease punishing economic sanctions and diplomatic pressure that are beginning to bite.