South Korean President Moon Jae-in held an emergency meeting with senior security officials on Thursday following President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE's decision to cancel talks with North Korean leader Kim Jong Un in Singapore, according to Yonhap News Agency.

"I am very perplexed and it is very regrettable that the North Korea-U.S. summit will not be held on June 12 when it was scheduled to be held," Moon said during the meeting at his residence, according to Yonhap.

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The South Korean leader also reportedly urged Kim and Trump to speak with each other following Trump's move.

"Denuclearization of the Korean Peninsula and the establishment of permanent peace are historic tasks that can neither be abandoned nor delayed," he added.

Moon's reported comments came after Trump said in a letter to Kim that he would not take part in the June 12 summit.

“I feel it is inappropriate, at this time, to have this long-planned meeting,” Trump wrote, citing Pyongyang's “tremendous anger and open hostility” toward the U.S.

Tensions between the U.S. and North Korea dramatically increased over the past week as both sides fought for leverage ahead of the talks.

Trump on Thursday left open the possibility for future meetings to take place if Kim takes “constructive” steps toward peace.

"It's possible that the existing summit could take place, or a summit at some later date,” the president said at the White House.