Speaking at a forum in Singapore on Friday, Moon said that Trump and Kim would “face the stern judgment of the international community” if their promises on denuclearisation were not kept.
“I believe the countries will honour the agreement reached by their leaders even if they face many difficulties in the process of working-level negotiations, because their leaders personally made a promise in front of the entire international community,” President Moon said, according to South Korea’s Yonhap news agency.
“If they do not keep the promise made by their leaders in front of the international community, they will have to face the judgment of the international community.”
Singapore was the host of a landmark summit between Trump and Kim last month when they agreed to work towards the denuclearisation of the Korean Peninsula, without describing when and how it would occur.
Follow-up talks between US Secretary of State Mike Pompeo and North Korean senior officials got off to a rocky start with Pyongyang accusing Washington of making “unilateral and gangster-like” demands.
On Friday, Moon, who met Kim twice this year, said that the North Korean leader has a “great desire to break away from the ideological confrontations” in the Korean Peninsula.
“If Chairman Kim Jong-un keeps his promise to denuclearise, he may be able to lead his country to prosperity,” Moon said.
But he also urged Pyongyang to come up with more details on their commitment to denuclearise.
When later asked by reporters whether the agreement between Trump and Kim would actually be implemented, Moon said the leaders “have no choice” but to carry out the agreement, according to Yonhap.
“What is completely different this time is that the leaders of the North and the US met directly and reached an agreement,” he added.
Moon also said that while negotiations will face “many bumps and bruises” along the way, he is confident a deal can be reached eventually.
Meanwhile, in Seoul, US and South Korean officials held a ceremony on Friday to return home the remains of two US servicemen killed during the 1950-53 Korean War.
Seoul’s defence ministry said the remains of an unidentified allied soldier, presumably American, found in South Korea in 2016, will be sent to the United States.
The US military has also brought to Seoul the remains of a South Korean soldier found in North Korea in 2001 during a joint search between the United States and North Korea, according to the Associated Press.
The ceremony came a day after talks between the US and North Korea over the return of US war remains were postponed tentatively to Sunday, according to the US State Department.
Following his talks with North Korea’s Kim in Singapore, Trump announced that the remains of American soldiers who died in North Korea would be repatriated to the US shortly. But since then, negotiations have stalled and the remains have not yet been turned over to the US.