This included the fact that North Korea recently objected to a joint military exercise between the US and South Korea despite pledging to tolerate such drills back in March.
Andrea Berger, an expert on North Korea's weapons program at Middlebury Institute of International Studies, said the letter's language is "cringe-worthy".
To his credit, Mr. Trump has accepted the urgency of solving the North Korean threat. 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.
On this occasion Trump wrote that he was praying to God the USA won't need to use its "massive and powerful" nukes.
"Whether the USA 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 said. "North Korea summit meeting per se but making such a meeting into an opportunity for progress on the nuclear and missile issues and above all the abductee issue", a foreign ministry statement said. In his tweet announcing the time and place of the now-cancelled summit, the president had said the meeting could be a "very special moment for World Peace".
It's also possible Mr. Trump got cold feet and wanted more time.
In his letter, he said Mr Kim should not "hesitate to call me or write" if he changed his mind about their now-cancelled summit.
"The United States will also have to undertake careful deliberations about the fate of the planned North Korea-U.S. summit in light of this provocative military ruckus jointly conducted with the South Korean authorities", North Korea's Korean Central News Agency said.
"North Korea has the opportunity to end decades of poverty and oppression by following the path of denuclearisation and joining the community of nations", Mr Trump said.
CNES AFP HONorth Korea plans to destroy its nuclear test facility as a goodwill gesture
"I hope that Kim Jong-un will ultimately do what is right, not only for himself, but perhaps most importantly what's right for his people, who are suffering greatly and needlessly."
But Democratic congressional leader Nancy Pelosi was scathing towards Trump's administration - blaming a lack of preparation for the summit collapse and judging Kim to be the "big victor".
China wasn't surprised by the collapse of the summit given recent signals that had come from Trump, a government official said.
"Over the past many days we have endeavoured to do what Chairman Kim and I had agreed, to put preparation teams together to begin to work for the summit, and we had received no response to our inquiries to them", Mr Pompeo said.
South Korean President Moon Jae-in played a major role in planning for the summit and sought to keep it on the rails in a visit to the White House this week.
The White House press secretary Sarah Huckabee Sanders told reporters in a daily briefing that the White House would wait for "concrete and verifiable steps" toward denuclearization in North Korea before the president would accept any invitation to meet.
UN Secretary-General Antonio Guterres said he was "deeply concerned".
He said, "Denuclearization of the Korean Peninsula and the establishment of permanent peace are historic tasks that can neither be abandoned nor delayed".
He said leaders had a responsibility to minimise the risk of weapons and said disarmament was a concern for every country and should cover weapons "from hand grenades to H-bombs".