He also ratcheted up his rhetoric on the North's human rights abuses in a speech to US service members at Yokota Air Base in Japan.
To facilitate the attendance of several senior functionaries from the North, South Korea has allowed some exemptions to sanctions imposed on North Korea over its nuclear programme, although the foreign ministry in Seoulsaid these would apply only during the Pyeongchang games. Not only did he broker an agreement to bring North Korea to the Winter Olympic Games in Pyeongchang; he convinced U.S. President Donald Trump that doing so was in fact Trump's idea.
North Korea says it is not interested in meeting with Vice President Mike Pence while he is in South Korea for the Winter Olympics. To that end he has invited the father of Otto Warmbier, an American student who died past year after being imprisoned in North Korea for 17 months, to join the Olympic delegation. Since it docked, North Korea has asked the South to provide oil for refuelling.
"I hope inter-Korean relations will improve but the question is what North Korea will do during the Olympics", he said.
On Wednesday, the North announced that Kim Yo Jong, the sister of dictator Kim Jong Un, would attend the games, joining the country's 90-year-old nominal head of state, Kim Yong Nam.
Kim Yo Jong, the sister of the North's leader, and her entourage will travel by private jet to Seoul's Incheon International Airport on Friday, North Korea told the South.
Unilaterally, the US has also targeted North Korean shipping companies and Chinese trading networks.
Pence has lambasted the North, announcing in Tokyo on Wednesday that the United States would impose its toughest sanctions to date on the regime. Moon has said he wants to build upon the Olympic outreach to restart talks with the U.S.to eventually halt North Koreas' nuclear development program in exchange for economic assistance and security guarantees. But Pyongyang indicated it is not interested in meeting with the Pence-led delegation.
North Korea might also seek to demonstrate its ability to retaliate should the USA seek to hobble Kim's nuclear weapons program with a limited - or "bloody-nose" - attack. The parade is understood to have been relatively low key.
Thursday's anticipated Army Day parade marks the 70th anniversary of founder Kim Il Sung's 1948 transformation of the revolutionary guerrilla force into a regular army. The North also cancelled its invitation for global media to the parade, in an apparent attempt to keep it low-key. Yet the event has unexpectedly caused problems between the host country and another nation before it has even begun - as Iran summoned Seoul's envoy in Tehran on Thursday in a dispute over smartphones and sanctions.
To be sure, the North Koreans will think they were invited to participate in the games not in spite of their nuclear program, but because of it.