A statement issued during global negotiations with North Korea in 2005 over its nuclear weapons development said the "United States affirmed that it has no nuclear weapons on the Korean Peninsula and has no intention to attack or invade (North Korea) with nuclear or conventional weapons".
Announcing the decision last month, Kim, while portraying the move as a friendly gesture by North Korea towards the United States and South Korea, also said the site was not necessary anymore because the nuclear weapons had been already been developed and no further tests were necessary, indicating that it was a credible nuclear power.
The former No. 2 man in the North Korean Embassy in London casts doubt on North Korean leader Kim Jong-un's new cuddly and approachable image in a new memoir published Monday.
North Korea for decades has been pushing a concept of "denuclearization" that bears no resemblance to the American definition.
The North Korea-watching 38 North website said in a report that imagery from May 7 showed that the process was "already well under way" at the site, which has been used for each of the North's six underground nuclear test explosions.
North Korea said it would allow journalists from the U.S., South Korea, China, Russia and Britain "on-the-spot coverage" of the ceremony.
The two leaders signed a joint statement that committed both to deepening ties and working towards reunification after the meeting on April 27, which saw Kim become the first North Korean leader to set foot in South Korea since the Korean War, which took place from 1950-1953 prior to an armistice agreement.
But no observers from worldwide atomic monitoring agencies have been invited, raising concerns over the openness of the process.
Over the years peaceful gestures made by the North Korean regime with respect to its nuclear program have not been particularly reliable.
The United States is pressuring North Korea to ship its nuclear weapons overseas before sanctions are lifted.
Pyongyang said last week it would dismantle the site on May 23-25.
The secretary said he was "convinced" Kim shared USA goals. "They have what they need so the way in which they collapse the tunnels is just show", said Melissa Hanham, senior research associate at the James Martin Center for Nonproliferation Studies. As such, it said, it would shutter the Punggye-ri site. There were reports the site had collapsed and was unusable, but Kim himself reportedly dismissed those claims, saying "we have two more tunnels that are bigger than the existing ones and that they are in good condition".
He said: "North Korea's definition of denuclearisation is different from the complete, verifiable, irreversible dismantlement that we think of".