National Security Council chief Chung Eui-yong and National Intelligence Service chief Suh Hoon fly to Washington on Thursday to brief U.S. President Donald Trump on their meeting with North Korean leader Kim Jong-un.
Chung and Suh met Kim in Pyongyang on Monday and said later that he is willing to talk about giving up his nuclear weapons.
"Chung will give Trump a detailed briefing on what Kim Jong-un said about denuclearization and U.S.-North Korea talks," a presidential official said on Wednesday.
Kim's offers "also include the release of three Americans detained in the North," a diplomatic source said.
Chung and Suh will also meet senior U.S. officials like White House National security adviser H.R. McMaster and CIA director Mike Pompeo.
Chung told reporters on Tuesday, "We have a separate North Korean message for Washington" but declined to say what it is.
Sources said the North promised to suspend its development of intercontinental ballistic missiles "depending on the U.S. attitude" as a precondition for talks with Washington.
The envoys quoted Kim as saying that denuclearization was his father Kim Jong-il's last wish and the North "said it would have no reason to possess nuclear weapons should the safety of its regime be guaranteed and military threats against North Korea removed."