SEOUL, May 1 (Xinhua) -- South Korean President Moon Jae-in asked the United Nations to observe the Democratic People's Republic of Korea (DPRK)'s planned shutdown of its nuclear test site, the Blue House of South Korea said Tuesday.

Kim Eui-kyeom, spokesman for Moon, told a press briefing that Moon had a phone conversation with UN Secretary General Antonio Guterres for half an hour from 11:30 a.m. local time (0230 GMT) to exchange opinions about the result of the third inter-Korean summit last week.

Moon told Guterres that top DPRK leader Kim Jong Un promised to transparently make open the closedown of the Punggye-ri nuclear test site to South Korea and the United States as well as to the international society.

The South Korean president asked the UN chief to allow UN officials to participate in the shutdown to observe and confirm it.

During the April 27 summit with Moon at the border village of Panmunjom, Kim said his country will openly close the Punggye-ri nuclear test site in northeast of the DPRK, where all of six nuclear tests were conducted, by the end of May.

After the summit, Moon and Kim signed and announced the Panmunjom Declaration in which the two sides agreed to the complete denuclearization and the change of the current armistice agreement into a peace treaty.

Moon told Guterres that the Panmunjom Declaration included an agreement to alter the heavily armed demilitarized zone (DMZ) into an actual peace zone, asking the UN to observe and verify the process of the alteration.

In response, Guterres said he was willing to cooperate in the process, noting that though Moon's calls require the approval from UN Security Council, he will make efforts to help settle peace on the Korean Peninsula.

The UN chief added that he will appoint a UN official in charge of arms reduction to cooperate with South Korea.

Moon also asked Guterres to issue a statement welcoming and supporting the Panmunjom Declaration by the UN General Assembly or the UN Security Council, saying the UN support will be a great help to improved inter-Korean relations and the success of the upcoming DPRK-U.S. summit.

The DPRK leader and U.S. President Donald Trump are forecast to hold the first-ever DPRK-U.S. summit in May or early June.