The top national security advisers of the United States, South Korea and Japan met at the weekend to discuss North Korea and the "complete denuclearisation of the Korean peninsula", South Korea's presidential Blue House said on Monday.
The two days of meetings could also help prepare the way for a possible meeting between U.S. President Donald Trump and North Korean leader Kim Jong Un.
They were the latest in a flurry of diplomatic activity spanning Asia, the United States and Europe ahead of North Korea's planned summits with the South and the United States.
South Korea's National Security Office chief Chung Eui-yong met U.S. National Security Adviser H.R. McMaster and Japan's National Security Adviser Shotaro Yachi to discuss summit meetings between Kim and South Korean President Moon Jae-in, the Blue House in Seoul said.
They also discussed the possible meeting between Trump and Kim, it said.
The security advisers from the three countries discussed the "complete denuclearisation of the Korean peninsula", agreed that "it was important to not repeat the mistakes of the past" and to work together closely, the Blue House said.
A senior North Korean diplomat left for Finland on Sunday for talks with former U.S. and South Korean officials, South Korea's Yonhap News Agency reported.
That followed three days of talks between North Korean and Swedish foreign ministers on security on the Korean peninsula.
Sweden "engaged heavily" on the issue of U.S. detainees during the talks between North Korean and Swedish foreign ministers, CNN reported on Sunday, citing unidentified sources with knowledge of the negotiations.
North Korea is pursuing its nuclear and missile programmes in defiance of U.N. Security Council sanctions and has made no secret of its plans to develop a missile capable of hitting the U.S. mainland.