In a rare step towards diplomacy between longtime enemies, a North Korean envoy making a rare visit to South Korea said his country is willing to open peace talks with the United States.

Kim Yong-chol, in South Korea for the end of the Olympics, said on Sunday North Korean leader Kim Jong-un wanted to improve ties with Washington and had "ample intentions of holding talks", according to the South's presidential office.

He made the remarks during a meeting with South Korean President Moon Jae-in, who is eager to engage the North after one of the most hostile periods in recent years on the Korean Peninsula.

In a statement on Sunday, the White House said Pyongyang would have to show it "is committed to achieving the complete, verifiable, and irreversible denuclearisation of the Korean Peninsula" if talks were to be held.

"We will see if Pyongyang's message today, that it is willing to hold talks, represents the first steps along the path to denuclearisation," it said. "In the meantime, the United States and the world must continue to make clear that North Korea's nuclear and missile programmes are a dead end."

Drive a wedge?

President Moon - who was invited a day after the opening ceremonies to Pyongyang for a summit with Kim Jong-un - also said Washington and Pyongyang should quickly meet to "fundamentally solve" the standoff on the peninsula.

Kim later sat in the VIP box at Olympic Stadium in Pyeongchang for the Olympic closing ceremonies, just metres away from US President Donald Trump's daughter, Ivanka, and the top US military commander on the peninsula, General Vincent Brooks.

Moon has yet to accept the North's invitation for a summit, but he has advocated engagement.

But he must first strike a balance with Washington, which has a policy meant to isolate and sanction the North until it agrees to give up its nuclear weapons. Some analysts believe Pyongyang is trying to drive a wedge to win concessions from Seoul.

Kim Yong-chol was head of the North's military intelligence when 2010 attacks on South Korea took place and is currently a vice chairman of the ruling party's central committee tasked with inter-Korea relations.

With decades of experience, he is one of the most powerful people in the North's ruling regime. Seoul decided to temporarily take him off of a blacklist to allow the visit.

Outside Olympic Stadium, just before the ceremony, more than 200 anti-Pyongyang protesters waved South Korean and US flags, banged drums and held signs saying "Killer Kim Yong Chol go to hell." They denounced the South Korean government's decision to allow the visit.