“He beat around the bush and failed to pull it through,” Mr Moon said about the former US president in an interview with the New York Times.
The South Korean president, who is scheduled to meet US president Joe Biden next month, said he hopes he would “go down as a historic” leader to have achieved substantive and irreversible progress on the stalled denuclearisation process.
Mr Moon said denuclearisation is a “matter of survival” for South Korea.
His statements come at the crucial time when the US president is scheduled to meet him next month and as Mr Moon serves his final year in office. The South Korean president helped broker two meetings between Mr Trump and North Korea’s leader, Kim Jong-un.
He criticised Mr Trump for failing to secure any long-term concessions from Pyongyang before pulling away from the second summit that was scheduled in Hanoi. The talks were stalled for almost two years and the two countries failed to reach an agreement on denuclearisation.
Mr Moon also said the deteriorating relations between China and America could possibly undermine the negotiations over denuclearisation.
“If tensions between the United States and China intensify, North Korea can take advantage of it and capitalise on it,” Mr Mood said urging Mr Biden to cooperate with Beijing.
Mr Moon urged the US to undertake a “mutually trusted road map” with North Korea.
“I hope that Biden will go down as a historic president that has achieved substantive and irreversible progress for the complete denuclearisation and peace settlement on the Korean Peninsula,” Mr Moon added.
The Biden administration is yet to disclose its foreign policy on North Korea but said its policy review was in the final stages.
Seen as provocations at the “low end of spectrum” by Biden administration officials, North Korea fired two short-range ballistic missiles last month in defiance to UN resolutions that have banned such launched by the country. The launch sparked concerns, with experts calling it a tactic to pressure the US president as it was the first such test after he took office.
Mr Trump indirectly defended his relationship with Mr Kim during a Fox News interview with Sean Hannity.
“I have a great relationship with a certain man that’s got great power over North Korea,” Mr Trump said.
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