Comments by US Vice President Mike Pence suggest the United States may be looking more favourably at diplomatic engagement with North Korea as South Korea considers a rare summit with its neighbour and long-time foe.

Pence said in a newspaper interview the United States and South Korea had agreed on terms for further diplomatic engagement with North Korea, first with Seoul and then possibly leading to direct talks with Washington.

The prospect of talks comes after months of tension between Pyongyang, Seoul and Washington over North Korea's nuclear and missile programmes, with US President Donald Trump and North Korean leader Kim Jong Un trading insults and threats of destruction amid tightening sanctions from the United Nations.

Speaking to the Washington Post aboard Air Force Two on his way home from the Games, Pence said Washington would keep up its "maximum pressure campaign" against Pyongyang but would be open to possible talks at the same time.

 "The point is, no pressure comes off until they are actually doing something that the alliance believes represents a meaningful step toward denuclearisation," Pence was quoted on Sunday as saying. "So the maximum pressure campaign is going to continue and intensify. But if you want to talk, we'll talk."

US Secretary of State Rex Tillerson said yesterday it was too early to judge whether latest developments represented the start of a diplomatic process.

"We've said for some time it's really up to the North Koreans to decide when they're ready to engage with us in a sincere way, a meaningful way," Tillerson told reporters in Egypt.

Last year, North Korea conducted dozens of missile launches and its sixth and largest nuclear test in defiance of UN Security Council resolutions as it pursues its goal of developing a nuclear-armed missile capable of reaching the United States.

Relations between the two Koreas have improved in recent weeks, with Pyongyang sending its highest ranking delegation ever to attend the Winter Olympic Games, being held in the South Korean resort of Pyeongchang.

South Korea said it would seek ways to continue engaging North Korea, including trying to arrange more reunions for families divided by the war and lowering military tensions.

The statement from the Ministry of Unification came after the North Korean delegation concluded its three-day visit.

"(The visit) shows that North Korea has a strong will to improve inter-Korean relations and that Pyongyang can make unprecedented and bold measures if deemed necessary," the ministry said.

Japan yesterday warned against being "blinded" by North Korea's diplomatic charm offensive at the Winter Olympics, saying the main goal remains ridding Pyongyang of nuclear weapons.