VIENNA (Reuters) – Irreversibly closing North Korea’s nuclear test site is an important step that could pave the way for progress at talks between U.S. President Donald Trump and North Korean leader Kim Jong Un, U.N. Secretary-General Antonio Guterres said on Monday.

North Korea gave details on Saturday on the planned dismantling of the Punggye-ri site where it is believed to have carried out all six of its nuclear tests.

The official Korean Central New Agency said it would take place between May 23 and 25 and involve collapsing all the site’s tunnels with explosions, blocking its entrances, and removing all observation facilities, research buildings and security posts.

“I would like to welcome that and to say that the irreversible closure of the site will be an important confidence-building measure that will contribute to further efforts towards sustainable peace and verifiable denuclearization of the Korean peninsula,” Guterres said in a statement after meeting Austria’s chancellor in Vienna.

“And I look forward to this positive momentum being consolidated at the summit between the leaders of the United States and North Korea,” he said in the remarks to reporters after his meeting with Chancellor Sebastian Kurz.

Trump and Kim are due to hold talks in Singapore on June 12, the first-ever meeting between a sitting U.S. president and a North Korean leader.

After North Korea’s announcement on Saturday, Trump said on Twitter: “Thank you, a very smart and gracious gesture!”

(Reporting by Francois Murphy; Editing by Toby Chopra)