The rogue regime's leader Kim Jong-Un also discussed similar plans with South Korea President Moon Jae-in.
Trump welcomed the North Korean announcement.
It followed a flurry of worldwide engagement with North Korea as the two Koreas held their own summit in late April and officials plan to hold high-level meetings in coming weeks.
"Thank you, a very smart and gracious gesture!" he wrote.
South Korea had no immediate response to the statement. It has always been the North's economic lifeline, but trade between the two has plummeted following its implementation of United Nations economic sanctions over North Korea's nuclear weapons and ballistic missile programs.
Besides local journalists, media representatives from South Korea, the United States, the UK, Russia and China will be allowed to witness the process to ensure the transparency although the number of media invitees was limited because of space constraint at the test side, North Korea's foreign ministry said in a statement, according to an AFP report. The exact date of the closure will depend on weather conditions, the agency said. North Korea will be "opening territorial airspace" to welcome the reporters.
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Mahathir said his four-party alliance will hold a meeting Saturday and name 10 ministers for a start. It was not clear when Anwar, who is now in hospital for treatment to his shoulder, would be freed.
Pompeo Friday promised the U.S. would work to rebuild North Korea's sanctions-hit economy if it agreed to surrender its nuclear arsenal.
North Korean Ministry of Foreign Affairs pledged transparency and laid out plans Saturday to dismantle the country's nuclear testing site.
North Korea has said the refusal of the nuclear program.
Above ground North Korea will block all entries to the site, and remove all guard posts, observation sites and research institutes, the report said. Kim refuted claims by Chinese scientists that parts of the site had been so badly damaged by previous explosions, particularly its sixth and last test in September, that it may now be unusable, Moon's office added. "So, it's a good confidence building measure, but not necessarily a sign of irreversible disarmament".