Video report by ITV News Reporter Olivia Kinsley
North Korea has pledged to shut down its nuclear testing facility in May in front of international experts, Seoul has said.
Kim Jong-un announced he would invite representatives from both South Korea and the US to witness the closure as the two Korean leaders met for a historic summit on Friday.
Details of the conversation were today made public by Yoon Young-chan, the spokesman for South Korea's president Moon Jae-in.
A permanent closure of the nuclear facility would be a landmark achievement in efforts to prevent nuclear proliferation and calm international relations between Pyongyang and the wider world.
Mr Moon and Mr Kim during the summit promised to work towards the "complete denuclearisation" of the Korean Peninsula, but had made no references to verification or timetables.
Mr Yoon said that the US President Donald Trump - who is due to hold his own meeting with Mr Kim within months - would see for himself that Mr Kim is “not a person” to aim missiles at America.
"Once we start talking, the United States will know that I am not a person to launch nuclear weapons at South Korea, the Pacific or the United States," Mr Yoon quoted Mr Kim as saying.
"If we maintain frequent meetings and build trust with the United States and receive promises for an end to the war and a non-aggression treaty, then why would be need to live in difficulty by keeping our nuclear weapons?" Mr Yoon quoted Mr Kim as saying.
Mr Trump has claimed he should be given credit for helping create a path towards the historic South Korea-North Korea summit.
Referring to preparations for a summit between himself and Mr Kim, expected in May of June, the US president earlier tweeted that “things are going very well”.
He now he faces a burden in helping turn the Korean leaders’ bold but vague vision for peace into reality after more than six decades of hostility.
Mr Trump must contend with a nagging suspicion about his own suitability to conduct that kind of war-and-peace negotiation and succeed where his predecessors have failed.
And then there is the question about whether Mr Kim really is willing to give up the nuclear weapons his nation took decades acquiring.
North Korea earlier this month announced it has suspended all tests of nuclear devices and intercontinental ballistic missiles and plans to close its nuclear testing ground.
The pledge came amid scepticism that the North would only be closing down the northernmost test tunnel at the site in Punggye-ri.
Some analysts say the tunnel has became too unstable to conduct further underground detonations following the country's sixth and most powerful nuclear test in September.
In his conversation with Mr Moon, Mr Kim denied that he would be merely clearing out damaged goods, saying that the site also has two new tunnels that are larger than previous testing facilities, Mr Yoon said.
He also apparently announced that North Korea plans to match time zones with its southern neighbour and historic adversary. The North created its own “Pyongyang Time” in 2015 by setting the clock 30 minutes behind the South.
The Friday summit between Mr Moon and Mr Kim kicked off a global diplomatic drive to deal with the North's nuclear and missile threats, which after a flurry of weapons tests last year involve purported thermonuclear weapons, developmental ICBMs and quick-fire solid-fuel missiles.
While the meeting ended with no new concrete measures on the nuclear stand-off, the more substantial discussions on the North's denuclearisation - including what, when and how it would occur - were always going to be reserved for a Kim-Trump summit.
The new round of nuclear negotiations with North Korea comes after a decades-long cycle of crises, stalemates and broken promises that allowed the country the room to build a legitimate arsenal.