Kono and the senior US officials agreed that Prime Minister Shinzo Abe's scheduled talks with Trump in early April will allow them to coordinate on issues related to North Korea, including the Trump-Kim summit.
The trip by Ri is being closely watched because there remains a huge amount of preparation that needs to be done and relatively little time before Kim is supposedly planning to sit down for summits with South Korean President Moon Jae-in and Trump.
"The two leaders expressed cautious optimism over recent developments and emphasised that a brighter future is available for North Korea, if it chooses the correct path". One can only wonder what the agenda for the meeting looked like before it was narrowed down.
Mr Pompeo, these officials said, has already been dealing with North Korean representatives through a channel that runs between the Central Intelligence Agency and its North Korean counterpart, the Reconnaissance General Bureau.
South Korean-born Yun, a strong advocate for engagement with Pyongyang, led contact with North Korea and quietly pursued direct diplomacy since taking his post under former President Barack Obama in 2016.
Sweden has long-standing ties with North Korea.
The planning is at "a very early stage", the official said. He had dinner with Wallström upon his arrival before heading to the North Korean Embassy, but talks continued on Friday, The Associated Press reported.
-North Korea summit scheduled for May and at the inter-Korean summit slated for late April at the truce village of Panmunjom.
A report on Friday by intelligence analysts at Jane's by IHS Markit said satellite imagery from February 25 showed gas emissions from a stack at the North's experimental light water reactor (ELWR), suggesting preliminary testing had likely begun.
In its statement, Sweden's foreign ministry noted that the U.N. Security Council had unanimously condemned North Korea's nuclear weapons and missile programmes and demanded their "complete, verifiable and irrevocable elimination".
His trip comes as U.S. President Donald Trump agreed last week to meet with North Korean leader Kim Jong Un by the end of May in an effort to achieve "permanent denuclearization" of the peninsula.
Ri is set to meet Swedish Foreign Minister Margot Wallstrom later Thursday or on Friday.
Swedish Prime Minister Stefan Lofven told his country's news agency TT that "if the main actors want Sweden to play a role then we are ready to do that".
Sweden's embassy in North Korea's capital, Pyongyang, represents U.S., Canadian and Australian interests and provides consular services in the country. And he has been in close touch with the director of South Korea's National Intelligence Service, Suh Hoon, whom USA officials said brokered Mr Kim's invitation to Trump. But with Trump's dismissal of Tillerson on Tuesday, Kono conferred with Sullivan, who is serving as the acting secretary. It was not known whether the two Asian ministers would meet Pompeo. So far, North Korea has yet to publicly comment on what it hopes to gain from the summits, adding an extra element of mystery and skepticism.
Both meetings are expected to focus on ways to rid the North of its nuclear weapons program.
The new images showing emissions rising from a reactor, which are said to be from February 25, bring into question the dictator-run state's seriousness about reducing its nuclear capability.
US State Department spokeswoman Heather Nauert told reporters in Washington that the US had yet to hear directly from Pyongyang on the planned summit.