"North Korea has announced that they will dismantle Nuclear Test Site this month, ahead of the big Summit Meeting on June 12th," he tweeted.

"Thank you, a very smart and gracious gesture!"

The site at Punggye-ri, in the northeast of the country, will be dismantled in front of foreign media between May 23-25 -- the latest in the North Korean leader's charm offensive.

Dialogue brokered by Seoul has seen US-North Korea relations go from trading personal insults and threats of war last year to a summit between Kim and President Donald Trump due in Singapore on June 12.

But sceptics warn that Pyongyang has yet to make any public commitment to give up its arsenal, which includes missiles capable of reaching the United States.

Washington is seeking the "complete, verifiable and irreversible denuclearization" of the North and stresses that verification will be key.

Punggye-ri has hosted all six of the North's nuclear tests, the latest and by far the most powerful in September last year, which Pyongyang said was an H-bomb.