Earlier, Kim Yo-jong, sister of North Korean leader Kim Jong-un, had visited the Cheong Wa Dae in Seoul and invited South Korean President Moon Jae-in to Pyongyang to conduct their first summit in more than a decade.
"The North Koreans should understand that for a summit or any kind of serious talks to occur, Moon needs to be able to take something to Washington - something that addresses denuclearization", he said before the North's invitation to Moon was announced.
North Korea's Choe Un Song takes part in the men's 1,500m short track speed skating heat event during the Pyeongchang 2018 Winter Olympic Games at the Gangneung Ice Arena in Gangneung on February 10, 2018.
South Korea earlier this year said the agreement failed to meet victims' needs and called for more steps, but Japan insists the agreement should not be changed.
China says it is committed to fully enforcing United Nations resolutions on North Korea, which include sweeping sanctions, but that all parties must make more effort to reduce tensions and get the talks process restarted.
Meanwhile, the DPRK media also lashed out at U.S. Vice President Mike Pence for his "anti-DPRK activities" when he was attending the opening ceremony, which Pyongyang said were aimed at disturbing the Olympics.
Mr Moon is eager to use Kim Yo Jong's presence at the games to restore regular communication with North Korea and eventually pull it into nuclear talks.
North and South Korea are technically still at war after their 1950-53 conflict ended in a truce rather than a peace treaty. Moon and Kim Yong Nam were due to be in the stands as well, a Blue House spokesperson told CNN.
During the game, North Korea's cheering squad chanted "we are one" and sang reunification songs, even as Korean pop music played throughout the stadium. But the prospect could sow division between the dovish leader, who has long argued for engagement with the nuclear-armed North to bring it to the negotiating table, and US President Donald Trump, who a year ago traded personal insults and threats of war with Kim.
North Korea has spent years developing its military, saying it needs to protect itself from US aggression.
In an effort to limit the fiery rhetoric of both leaders, the US and South Korea agreed to suspend military exercises in the region for the duration of the Olympics.
"The Vice President is grateful that President Moon reaffirmed his strong commitment to the global maximum pressure campaign and for his support for continued sanctions", said Pence's spokeswoman, Alyssa Farah.
But it carried seven front page pictures on the departure from Pyongyang and arrival in Seoul of its diplomatic delegation to the Winter Olympics, led by ceremonial head of state Kim Yong Nam and including the leader's sister Kim Yo Jong.
Pence said Friday the US would oppose talks between the two Koreas until the North agreed to open negotiations on ending its nuclear program.
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