Deputy Secretary John Sullivan met separately with Foreign Minister Kang Kyung-wha of South Korea, the nation that broached the Trump-Kim summit, and Foreign Minister Taro Kono of Japan, whose nation is more skeptical about the sudden spirit of rapprochement.
"To this end, we've made a decision to prepare for it focusing on the agenda of the denuclearization on the Korean peninsula, a permanent peace settlement including easing military tensions dramatically, and fresh and bold progress in South-North relations".
In an interview with US broadcaster PBS that aired Friday, she said that she believes a "breakthrough" on denuclearization is possible in talks between the USA and North Korea.
North Korea's foreign minister has attended talks in Stockholm with Sweden's Prime Minister Stefan Lofven, ahead of a possible meeting between US President Donald Trump and Kim Jong-un.
Even amid North Korea tensions, Trump has repeatedly denounced a United States free trade deal with ally South Korea as "unfair" and threatened many times to scrap it.
Mr Suh was one of two South Korean envoys who visited the White House last week to brief Mr Trump on their meeting with Kim Jong Un in Pyongyang a few days earlier.
Ri's surprise trip to Stockholm has taken on added significance due to expectations that a Trump-Kim summit could defuse the tensions over North Korea's nuclear weapons program. So far, North Korea has yet to publicly comment on what it hopes to gain from the talks.
"We've never been in a position where a president - our president - has met with a leader of North Korea, ever".
He said Japan, the US and South Korea will respond in a coordinated manner, so that no differences will emerge in their positions.
Abe and Moon also agreed to work together to hold a proposed trilateral summit of leaders from Japan, China and South Korea at an early date and resume so-called shuttle diplomacy between Japanese and South Korean leaders.
Donald Trump last week accepted an invitation for direct talks with Mr Kim, a shock announcement from the two leaders who have traded threats and insults for months.
So the visit has prompted speculation it might be part of preparations for the US-North Korea summit.
Some reports have suggested that Japan is less optimistic than its allies in Seoul and Washington that the talks are a good idea, but U.S. officials said talks with both Kono and Kang at the State Department had gone well.
"We believe in dialogue and the political process, but we are not naïve", Wallstrom said. "We've been working with North Korea". "I just think we have to go into this with eyes wide open".
In addition to the summit, South Korea agreed to dispatch its artists and Taekwondo demonstrators to Pyongyang in return for the DPRK's dispatch of its art troupe and demonstration team to the 23rd Winter Olympics hosted by South Korea's Pyeongchang county in February.
"They now have nuclear weapons and a delivery system that can legitimately threaten all states in the United States", Yun told CNN on Thursday about the North.