SEOUL — President Moon Jae-in of South Korea said Wednesday that he and President Trump could sit down for a three-way summit meeting with Kim Jong Un if their individual meetings with the North Korean leader on denuclearizing his country proceed well in the coming weeks.

Moon and Kim are planning an inter-Korean summit in late April at Peace House, a South Korean conference hall inside Panmunjom, the so-called truce village that straddles the Demilitarized Zone, or DMZ, separating the two Koreas.

That meeting is expected to be followed by a planned Trump-Kim summit meeting by May.

If that meeting takes place, Trump will be the first-ever sitting U.S. president to meet a North Korean leader; Washington and Pyongyang are still technically at war because the 1950-53 Korean War was halted with a truce rather than a peace treaty.

In other developments Wednesday on the Korean nuclear issue:

■ Finnish officials said delegates from North Korea, South Korea, and the United States concluded ‘‘constructive’’ unofficial diplomatic talks in the Nordic country that were widely believed to be laying the groundwork for the upcoming meeting between the Koreas and the proposed US-North Korea summit.

The foreign ministry said in a brief statement said that the tripartite talks were held in a positive atmosphere and were aimed at ‘‘building confidence and reducing tensions on the Korean Peninsula.’’

Eighteen delegates, six from each country, plus observers from the United Nations and Europe attended the secretive two-day talks at a 19th-century manor house just outside Helsinki.

Media were largely kept in the dark about the identities of the delegates and issues on the table, apart from Finnish Foreign Minister Timo Soini saying Tuesday that denuclearization wasn’t on the agenda.

What is known, however, is that senior North Korean diplomat Choe Kang Il, who handles North American affairs for his government, was among delegates from Pyongyang, while the US delegation is believed to have included Kathleen Stephens, the former ambassador to South Korea.

■ The UN Security Council voted unanimously to extend the mandate for UN experts monitoring sanctions against North Korea.

The resolution adopted emphasizes ‘‘the importance of credible, fact-based, independent assessments, analysis, and recommendations’’ by the experts, who recently reported that Pyongyang is flouting embargoes by sending Syria banned items for ballistic missiles and chemical weapons. Their work was extended until April 24, 2019.

In Seoul, Moon attached great significance to the venue for his coming meeting with Kim.

“The North Korea-United States summit, which will follow the inter-Korean summit, will itself be a momentous event in world history,’’ Moon said.

Material from the Associated Press was used in this report.