Guterres welcomed the announcement by North Korean leader Kim Jong Un during a summit with his South Korean counterpart Moon Jae-in in Pyongyang.

"The commitments reflected in the joint statement include important military confidence-building measures and a commitment by the DPRK to dismantle missile engine testing infrastructure in the presence of experts from related countries," Guterres said in a statement.

"Now it is time for concrete action."

When North Korea dismantled a nuclear test site in May, Guterres complained that no international experts had been on hand to witness the closure.

North Korea also expressed readiness to close its Yongbyon nuclear plant, which is key to its weapons program, if Washington takes "corresponding measures."

Guterres offered UN help to advance efforts to fully rid the Korean peninsula of nuclear weapons and called for unity among global powers.

The breakthrough at the Pyongyang summit came amid preparations for next week's annual gathering at the United Nations of world leaders, during which North Korea will loom large.

US Secretary of State Mike Pompeo has invited North Korean Foreign Minister Ri Yong ho for talks in New York, on the sidelines of the UN General Assembly meeting.

Pompeo said the talks in New York and meetings in Vienna will be the beginning of negotiations on the denuclearization of North Korea, to be completed by 2021.

Pompeo will chair a Security Council meeting next week on North Korea to discuss US diplomatic efforts that have undergone a major shift in tone from last year.

At last year's UN gathering, President Donald Trump threatened to totally destroy North Korea and derided Kim as "little rocket man."

The Trump administration is facing calls from Russia and China to consider easing tough economic sanctions imposed on North Korea to create an incentive for Pyongyang to move forward.

The United States maintains that sanctions must remain in place until North Korea has fully dismantled its weapons programs.