Preparations for the still-unconfirmed meeting between President Donald Trump and North Korean dictator Kim Jong-un are moving ahead, as the South Korean government said on Friday it is working to expedite both a summit with North Korea and a meeting between Trump and President Moon Jae-in.

Meanwhile, North Korea’s Foreign Minister was spotted in Sweden, prompting speculation that he was doing advance work for Trump and Kim to meet there.

Trump spoke with Moon on Friday and said he still plans to meet with Kim by the end of May, according to Reuters.

Both the U.S. and South Korean presidents were described as cautiously optimistic that diplomacy could resolve the North Korean nuclear missile crisis. They also both stressed that North Korea needed to take concrete steps toward disarmament, and would not be allowed to use the spring summits as a delaying tactic while it forges ahead with weapons research.

President Moon’s chief of staff Im Jong-seok spoke of holding a meeting between North and South Korean officials in March that would help pave the way for Moon to meet with Kim Jong-un.

Im said the agenda for the North-South meeting would be “narrowed down” to “denuclearizing the Korean peninsula, securing permanent peace to ease military tension and new, bold ways to take inter-Korean relations forward.” Those are rather heavy topics. One can only wonder what the agenda for the meeting looked like before it was narrowed down.

Reuters notes that Trump’s telephone conversation with Moon also covered U.S.-South Korean trade issues, with Trump asking South Korea to “show flexibility” in negotiations and seeming to stand by his assessment of current trade agreements as “unfair” to the United States.

North Korean Foreign Minister Ri Yong Ho arrived in Stockholm on Thursday for meetings with both Swedish Foreign Minister Margot Wallstrom and Prime Minister Stefan Lofven.

Lofven’s office refused to discuss the details of his meeting with Ri, but there is wide speculation in the media that Sweden could either host the Trump-Kim summit or assist with setting it up elsewhere. The Swedish embassy in Pyongyang has long facilitated diplomatic contact between North Korea and the United States, which does not have an embassy there.

“The whole world is naturally following the situation on the Korean peninsula. It is important, for security reasons it is of interest to us all. What is needed now is dialogue and we are happy to have this meeting. But we are not naïve and think that we can resolve all the problems of the world. It is up to the parties to decide how to go forward,” Wallstrom told reporters on Friday.

“If the main actors want Sweden to play a role – facilitate, be a forum or a link or whatever it may be—then we are ready to do that,” Prime Minister Lofven said in a separate interview.

“This is such an incredibly important issue. We are a country that is militarily non-aligned and have a longstanding presence in North Korea, and with the trust we enjoy we think we can play a role. But it has to be the main actors who decide which role Sweden will play,” he stressed.

The BBC describes the agenda for Ri’s surprise visit to Sweden as “broadening” to include “confidence-building measures with the U.S., including the release of U.S. citizens from North Korean detention.” The discussion is apparently going well enough for Ri to extend his stay for a few days.

The New York Times finds significance in the presence of Choe Kang-il, North Korea’s deputy director for North American affairs, as part of Ri’s mission to Sweden.

Also meaningful is South Korean Foreign Minister Kang Kyung-wha’s arrival in Washington on Thursday. Kang more-or-less openly said she was in D.C. to make sure the Trump-Kim meeting is still on track after the sudden dismissal of Secretary of State Rex Tillerson this week. Tillerson’s apparent replacement, former CIA Director Mike Pompeo, is seen as more skeptical of negotiations with North Korea than Tillerson was.