But after a flurry of diplomatic overtures eased tension in recent months, the two leaders are now headed for a history-making handshake that USA officials hope could eventually lead to the dismantling of a North Korean nuclear programme that threatens the United States.
Secretary of state Mike Pompeo is the highest-ranking official on the list who has met Kim before.
The White House also announced Trump would be leaving Singapore earlier than previously expected and holding a media availability ahead of his departure.
Considering that both the North Korean leader and the United States president are expected to depart Singapore quickly after the summit, Rodman might be making the trip here for nothing after all.
A suite on the 20th floor of St. Regis Hotel, where Kim is staying, costs more than 13,000 Singaporean dollars a night.
For Kim, about half Trump's age and representing the third generation of North Korea's ruling dynasty, the summit affords both him and his long-isolated country the global legitimacy his father and grandfather could only dream of.
Exactly what role will he play in the US-North Korea talks, due to take place at Capella Hotel at 9am today?
A man watches a TV screen showing file footage of US President Donald Trump (right) and North Korean leader Kim Jong Un during a news programme at the Seoul Railway Station in Seoul, South Korea.
AFP 2018 Saul Loeb World Follows Every Step of Historic Trump Kim Summit
However, it now appears that the U.S.is confident tings are going smoothly.
Trump and his senior officials have in recent weeks been referring to Kim as "Chairman".
"It is our contribution to an global endeavor which is in our profound interest", he told reporters on Sunday.
The real North Korean leader and Trump arrived in Singapore on Sunday.
"Wide-ranging and profound views on the issue of establishing new DPRK-US relations, the issue of building a permanent and durable peace-keeping mechanism on the Korean Peninsula, the issue of actualizing the denuclearization of the Korean peninsula and other issues of mutual concern" will be discussed, state-run KCNA reported early Monday. As I recently wrote, while certain sanctions on North Korea are discretionary, a key 2016 law specifically obligates the president to sanction people and entities complicit in human rights abuses in North Korea - not just those involved in weapons proliferation - and the Trump administration legally can't suspend sanctions more broadly unless North Korea implements key human rights reforms. The war was concluded with a truce, not a peace treaty, but a treaty will also have to include China, which was party to the armistice.
Laboriously negotiated past nuclear deals, considered breakthroughs at the time, broke down on North Korea's extreme sensitivity to allowing in outsiders to look at whether they're dismantling their nuclear facilities, many of which are thought to be hidden. Meanwhile, Mr Kim has called Mr Trump "mentally deranged" and a "dotard".
He said about half of the cost is for security. North Korea has always been a useful buffer between China and US forces in South Korea.
Interested in North Korea?
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Trump has long argued that the U.S. is trapped in a number of trade deals that put the country at a competitive disadvantage. Canada and Mexico, the other members of the 1994 pact, have been frustrated by the slow pace of talks to renegotiate NAFTA.