US ties any North Korea talks to nuclear arms
The United States says any dialogue with North Korea must have nuclear disarmament as the end goal.
The North indicated on the last day of the Winter Olympics in Pyeongchang it was ready for talks, according to South Korea.
North Korea has previously said it will not accept any preconditions.
"We will see if Pyongyang's message... that it is willing to hold talks, represents the first steps along the path to denuclearization," the US said.
Reports about the North's willingness to speak to the US emerged after a meeting of its officials with the South Korean president before the Games' closing ceremony on Sunday.
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US President Donald Trump's daughter Ivanka also attended the ceremony but she is not expected to talk with any North Koreans, even though she sat a few feet from their main envoy, Gen Kim Yong-chol, at the Olympic Stadium.
North Korea's mixed messages
North Korea was "very willing" to hold talks with the US, said the office of South Korean President Moon Jae-in.
It added that the North had "agreed that inter-Korea talks and North-US relations should improve together".
The revelation from the South Korean presidency came hours after a furious statement from the North that described fresh sanctions announced by Washington as "an act of war".
Pyongyang's foreign ministry praised the way the two Koreas had co-operated together during the Olympics but said the US had "brought the threat of war to the Korean peninsula with large-scale new sanctions".
The Korean peninsula has been divided since the 1950-53 war and the two sides have never signed a peace treaty.
The rapprochement between the two Koreas has been seen as a move by the North to drive a wedge between the South and the US.
Experts have cautioned that the latest developments do not put an end to underlying regional tensions, particularly following last year's nuclear and missile tests carried out by the North.
Could there be a breakthrough this time?
South Korean media is abuzz with suggestions that North-US talks could still take place while the respective delegations are in town.
The BBC's Laura Bicker, in Pyeongchang, asked an official from South's government if the meeting could take place in the next two days, and the answer was: "We will see."
North Korea has sent an eight-person team across the border, including Gen Kim Choe Kang-il, a senior diplomat handling North American affairs.
Meanwhile, Allison Hooker - a Koreas specialist from the US National Security Council - is part of the US delegation. She met Gen Kim in 2014 in North Korea, as the US tried to free two American detainees.
The scene could be set for a more low-key meeting than a failed attempt with US Vice-President Mike Pence.
He had been set to meet Kim Yo-jong, the sister of North Korean President Kim Jong-un, at the start of the Games but the meeting was cancelled inexplicably by the North Koreans, according to the US officials. North Korea made no comment.
There has been no official interaction between North Korea and the Trump administration.