South Korean President Moon Jae-in expressed regret early Friday over President Donald Trump's decision to call off his summit with North Korean leader Kim Jong Un and urged the pair to hold direct talks, Seoul's presidential office said.

At an emergency national security meeting, Moon said it was "deeply regrettable that the U.S.-North Korea summit will not take place as scheduled" after Trump pulled out of the high-stakes talks arranged for June 12 in Singapore.

"The denuclearization of the Korean peninsula and permanent peace is a historic task that cannot be given up or delayed," Moon said, adding that it would be difficult to resolve thorny diplomatic issues through the current method of communication between the US and North Korea.

"I hope that the leaders resolve the issue through more direct and close dialogue between themselves," he said.