South Korea President Moon Jae-in says he is "baffled and very regretful" that President Donald Trump cancelled the planned meeting with North Korean leader Kim Jong Un in Singapore that had been set for June 12.

South Korea did not have any advance notice and was caught off guard Thursday by the cancellation, according to the country's presidential office.

Urging both leaders to resolve the issue "by direct and closer conversations," Moon noted that "it is difficult to solve the sensitive and difficult diplomatic problems through the current way of communication," the presidency, called the Blue House, said in a statement.

"Denuclearization on the Korean Peninsula and permanent peace is a historic task that could not be given up, nor delayed," he said in the statement after an hour-long emergency National Security Council meeting.

South Korean President Moon Jae-in and President Donald J. Trump shake hands during a meeting at the White House in Washington, May 22, 2018.(YONHAP/EPA via Shutterstock) South Korean President Moon Jae-in and President Donald J. Trump shake hands during a meeting at the White House in Washington, May 22, 2018.

Trump said in a letter to Kim Thursday that it would be "inappropriate" to hold the summit next month as planned because of what he called "tremendous anger and open hostility" in a statement this week from a North Korean official.

The cancellation, Trump said in remarks later in the day, was a "tremendous setback for North Korea and, indeed, a setback for the world."

There were split opinions among residents in South Korea on the cancellation of the summit, some backing up Trump's surprising move Thursday.

“Trump said he won’t have talks? Why?” A food vendor named Choi Young-sook asked. “I think [Trump] cancelled the meeting because he expects more from North Korea. He is trying to get a head start.”

North Koraen Leader Kim Jong Un speaks during the Inter-Korean Summit at the Peace House on April 27, 2018 in Panmunjom, South Korea.(Korea Summit Press Pool/Getty Images) North Koraen Leader Kim Jong Un speaks during the Inter-Korean Summit at the Peace House on April 27, 2018 in Panmunjom, South Korea.

“President Trump showed off his negotiating skills this time, by not being swayed by North Korea’s continuous threats and breaking promises,” said Cho Youngtak, a psychiatry resident in Asan Medical Center in South Korea. “In the long term, the decision will bring South Korea and U.S. to a better position in bargaining.”

Meanwhile, some people were frustrated that the historic meeting was called off.

“I thought [the] North Korea-U.S. summit would bring peace to Korea,” a college student Lee Myoung Suk said. "It would have ended in a greater peace if South Korea joined for a three-party talk."

“But when will be the appropriate time?” a Malaysian student attending a South Korean university asked, while a local engineer added, “There is always turmoil, so sooner is better than later.”

General view of central business district on May 11, 2018 in Singapore.(Ore Huiying/Getty Images) General view of central business district on May 11, 2018 in Singapore.