Guterres will pay an official visit to South Korea next week for talks with leaders in Seoul and to attend the opening ceremony of the Olympic Games in Pyeongchang.

"Our objective remains the peaceful denuclearization of the Korean peninsula," Guterres told reporters at UN headquarters.

"For that, it is absolutely essential that serious discussion take place among the key actors in this process and the UN will do everything possible to encourage them in that regard," he said.

After a series of threatening missile tests, North Korea last month agreed to hold talks with the South and send its athletes to the Winter Olympic Games, easing tensions.

The United States, however, dismissed the moves as a distraction and pressed on with a campaign to pressure North Korea to abandon its nuclear ambitions.

Led by the United States, the Security Council has imposed three sets of tough economic sanctions on North Korea to cut off revenue to its military programs.

After offering to hold unconditional talks with Pyongyang, US Secretary of State Rex Tillerson stepped back from the offer, telling the Security Council last month that North Korea must earn its place at the negotiating table.

Guterres said the unity of the council in unanimously agreeing to slap sanctions "has created the conditions" for addressing the North Korean nuclear threat "through diplomatic engagement."

North Korea's Foreign Minister Ri Yong Ho wrote to Guterres this week to ask him to help keep the momentum for improved relations by opposing plans for US-South Korea military drills to be held after the Olympics.

Spokesman Stephane Dujarric has not ruled out that the UN chief could meet with a North Korean official during his visit to South Korea.