At 11:30 p.m., Moon summoned his top national security and foreign affairs officials including National Security Office chief Chung Eui-yong. Chung, who had accompanied Moon to Washington had stated earlier that he considers the US-North Korea summit to be "99.9 percent" set.

In a letter addressed to Kim revealed by the White House Trump said that the meeting would be inappropriate at present.

“Sadly, based on the tremendous anger and open hostility displayed in your most recent statement, I feel it is inappropriate, at this time, to have this long-planned meeting,” Trump said in the letter.

“Therefore, please let this letter serve to represent that the Singapore summit, for the good of both parties, but to the detriment of the world, will not take place.”

Trump went on to address North Korea’s reference to its nuclear capabilities saying that that of the US is “so massive and powerful that I pray to God they will never have to be used.”

Trump went on to thank Kim for the release of three US citizens, and inform the North Korean leader “do not hesitate to call me or write” if there are changes in Pyongyang’s stance regarding the summit.

Earlier in the day, North Korea issued a statement threatening to call off the meeting, and implying possibility of military conflict involving nuclear weapons with the US.

Whether the US will meet us at a meeting room or encounter us at nuclear-to-nuclear showdown is entirely dependent upon the decision and behavior of the United States,” Choe Son-hui, North Korea’s vice foreign minister, said in a statement carried by the state-run Korean Central News Agency.

Choe threatened to make a suggestion to the country’s “supreme leadership” to reconsider the summit, if the US continues to cling “to unlawful and outrageous acts.”

By Choi He-suk and Jung Min-kyung (cheesuk@heraldcorp.com) (mkjung@heraldcorp.com)