Trump and Kim are due to hold talks in Singapore on June 12, the first-ever meeting between a sitting US president and a North Korean leader.
The US Acting Assistant Secretary of State for East Asian and Pacific Affairs, Susan Thornton, was speaking in Tokyo on Tuesday in a seminar organized by the Wall Street Journal.
It will mark the first summit between a sitting U.S. president and a North Korean leader.
North Korea announced last month that it "no longer need [s]" nuclear and missile tests because the country has "verified the completion of nuclear weapons".
Commercial satellite imagery shows North Korea has begun dismantling its nuclear test site, according to an analysis from a prominent worldwide monitor.
"Dismantlement of the nuclear test ground will be done in the following sequence-making all tunnels of the test ground collapse by explosion; completely blocking entries; removing all observation facilities, research institutes and structures of guard units on the ground", the ministry said in a statement released through the state run Korean Central News Agency.
The dismantling of the mountainous complex, which has been the site of all six nuclear tests conducted by North Korea since 2006, is part of its promise to stop nuclear and intercontinental ballistic missile tests ahead of the first-ever U.S.
The newspaper said the Punggye-ri site, situated near Mount Mantap in northeastern North Korea, was "wrecked" beyond fix by a landslide.
The shutdown process will unfold under the presences of journalists, including those from the USA and South Korea.
Families behind Indonesia bombings belonged to same religious study group
According to CNN , Indonesia has seen an increase in terrorist attacks beginning in 2014, mirroring an earlier trend in 2001. At Surabaya Centre Pentecostal Church, Futrianto then drove his vehicle onto the church grounds and detonated explosives.
The North also is widely believed to have as many as 60 nuclear weapons and production facilities that were not affected.
"It is North Korea's diplomatic tactic to push the situation to extreme confrontation and suddenly send peace gestures".
He said that "one advantage" of having the U.S.
The United States is pressuring North Korea to ship its nuclear weapons overseas before sanctions are lifted. The summit will give Trump an early chance "to size Kim Jong Un up and see if the commitment is real", he said. Pompeo, speaking on CBS News' "Face the Nation" on Sunday said that the regime will benefit from private investment, not assistance from USA taxpayers, in exchange for abandoning its nuclear weapon program.
Suh Kyun-ryul, a professor of nuclear engineering at Seoul National University, agreed that the test site could contain residual nuclear material, saying the inspection process should come first, before shutting down the test site.
During their meeting at a border truce village, Mr Moon and Mr Kim vaguely promised to work towards the "complete denuclearisation" of the Korean Peninsula, but made no references to verification or timetables.
Pyongyang has long wanted to see an end to the USA military presence in - and nuclear umbrella over - the South, but it invaded its neighbour in 1950 and is the only one of the two Koreas to possess nuclear weapons.
But while Pompeo elaborated that Washington is "always concerned about human rights", he said, "it's the case not only are there political prisoners that remain in North Korea, there are Americans held around the world by other rogue regimes too". "That's what the president is going to say".
David Beasley said he had enjoyed unprecedented access to the secretive state, telling BBC radio that North Korea's leaders had a "sense of optimism".