Kim, meanwhile, has received a reception usually only experienced by rockstars, with crowds fighting to see him as he toured Singapore overnight. About 100 reporters and Singapore residents shouted his name and took pictures with phones as Kim visited Marina Bay Sands resort, famed for its rooftop infinity pool overlooking the city.
He joined Singapore's foreign minister, Vivian Balakrishnan, who tweeted a selfie with a smiling Kim and Singapore Education Minister Ong Ye Kung, against a backdrop of flowers with the hashtag #Guesswhere.
"There's a special place in hell for any foreign leader that engages in bad-faith diplomacy with President Donald J. Trump and then tries to stab him in the back on the way out the door", said United States trade advisor Peter Navarro.
Addressing reporters on Monday, U.S. Secretary of State Mike Pompeo sought to keep expectations in check, saying: "We are hopeful this summit will have set the conditions for future successful talks". That armistice has yet to be replaced with a peace treaty, leaving the peninsula in a technical state of war.
It would be the first meeting between a sitting US president and a North Korean leader since the end of the 1950-53 Korean War.
"We've got a very interesting meeting ... tomorrow, and I just think it's going to work out very nicely", Trump said. He left early, and as he flew to Singapore, he tweeted that he was yanking the USA out of the traditional group statement.
Armed police are guarding the St Regis Hotel on the island of Sentosa where he is staying. "We don't know. Kim might also want security assurances from China, Russia, and the United Nations Security Council", Kovrig said.
Trump had been scheduled to fly back to Washington on Wednesday morning after spending Tuesday with the North Korean leader in Singapore.
"There are only two people that can make decisions of this magnitude".
For the US president, the reality show-like pageantry of the Singapore summit is the chief concern. Others complained about the traffic jams in downtown Singapore.
Mr Lee said the cost was worthwhile.
"It is our contribution to an global endeavour which is in our profound interest", he told reporters.
Despite the White House releasing on 24 May a letter from US President Donald Trump to North Korean Supreme Leader Kim Jong-un stating that Trump was withdrawing from the summit, preparatory talks resumed and Trump and Kim arrived in Singapore on 10 June.
A group of North Korean security staff were seen coming back into the hotel with cardboard boxes, one with McDonald's takeaway. It heralded the summit as part of a "changed era". The Koreans, in the North and in the South, understand that, and the inter-Korean 'Panmunjom Declaration" of 27 April focusses not on denuclearisation (although that is one of the stated goals) but on the two Koreas" "firm commitment to bring a swift end to the Cold War relic of longstanding division and confrontation", transforming the "unnatural state of armistice' into a "robust peace regime'.