First Daughter Ivanka Trump was in the crowd for the ceremony.
A South Korean protester tear a North Korean flag with a knife, during a rally against a visit of Kim Yong Chol, vice chairman of North Korea's ruling Workers' Party Central Committee, near the Unification bridge in Paju, South Korea, Sunday, Feb. 25, 2018.
The North's high-level delegation led by Kim will include foreign ministry officials who handle relations with the USA and the nuclear issue, raising hopes that Pyongyang is willing to discuss the nuclear issue during this visit, Yonhap news agency said. During Vice President Mike Pence's recent trip to South Korea's Winter Olympics, he and South Korean President Moon Jae In visited a memorial of the incident, which includes a salvaged hull of the ship.
American athletes are bringing home 23 medals, putting the U.S.in fourth place overall.
Gen. Kim has been accused of orchestrating attacks on the Cheonan warship and Yeonpyeong Island in 2010, leading to the death of 46 South Korean sailors.
The U.S. delegation included National Security Council (NSC) director for Korea Allison Hooker.
"As we have stated on numerous occasions, we will consider any type of blockade an act of war against us, and if United States has indeed the guts to confront us in "rough" manner, we will not necessarily take the trouble to stop it", said a foreign ministry spokesman quoted by the official KCNA news agency.
But despite a nod to North Korean-US talks, the regime still appeared to launch its usual barrage of threats.
"The delegation congratulated [Moon] on an incredible Olympic Games and applauded throughout the ceremonies including for the US and South Korean athletes", said a senior Trump administration official briefing reporters in Pyeongchang. She has said the goal of her visit is to advocate maximum pressure on North Korea to halt its nuclear program.
But Moon did not immediately accept an invitation passed on by Kim Yo Jong from her brother to a summit in Pyongyang, saying the right conditions must be created.
Trump warned that if the latest sanctions do not work, the United States may "go to phase two", which he did not define but said "may be a very rough thing".
Moon won election previous year after promising to engage North Korea in an effort to ease tensions on the Korean Peninsula.
Just before the Olympic closing ceremonies, Moon's office issued a statement confirming the South Korean president met with Gen. Kim, who expressed North Korea's "willingness" to open talks with the United States.
North Korea and the U.S., however, had each dismissed the possibility of any interaction between their officials. She said North Korea has a bright path ahead of it if it chooses denuclearization. "We will keep standing strong until North Korea stops threatening our country, our allies or until they abandon their nuclear and ballistic missiles once and for all". "If we can't, something will have to happen", Trump said.