Kim called Trump "a mentally deranged USA dotard".
After a flurry of contacts between the two Koreas, South Korean officials suggested to Trump in March that Kim would be willing to meet face-to-face and the US president agreed.
"If that's the case, Beijing will have a role to play on how to implement the deals", said Cheng Xiaohe, an associate professor of global relations at Renmin University in Beijing.
"The fact that we have been chosen as the site of the meeting, we did not ask for it.it says something about Singapore relations with the parties. and our standing in the worldwide community", he added.
Enemies since the 1950-53 Korean War, leaders of North Korea and the United States have never met previously - or even spoken on the telephone. Using satellite imagery, defector interviews, media reports and other sources, the department found between 182 and 490 detention facilities spread across North Korea.
Trump and Kim lookalikes held a summit of their own at a local shopping mall, while one bistro is offering a libation known as the Trump-Kim "Bromance:" Beer, tequila, diet Coke and the Korean distilled rice liquor known as soju.
The two men are scheduled to meet in Singapore on Tuesday. A Japanese official said the country would be willing to provide aid to North Korea in exchange for the release of the captives and resolution of the nuclear issue.
After fiery rhetoric between North Korea and the USA last year, Kim declared in his New Year's address that the country's weapons program was complete. However, the South Carolina Republican noted that he is "not here to spread democracy" or to unite the North with South Korea.
But, barring a shock last minute development, the historic meeting between the U.S. and North Korean leaders will go ahead.
The US hopes the summit will kick-start a process that eventually sees Kim give up nuclear weapons. China has repeatedly said that the root of the nuclear crisis needs to be dealt with by Pyongyang and Washington and that a summit between the two sides could be a "key step" to resolving the situation. But after some diplomatic scrambling, the two leaders will now sit down together.
Officers combed the city on Sunday, from the old colonial section to the modern skyscrapers to the hotel on nearby Sentosa island where Trump and Kim will actually meet. That would be illegal, under the 2016 law, unless North Korea also agrees to key human rights reforms. But the success or failure of the summit will be seen by some as an indication of China's status as a major player in Northeast Asia, something Beijing has long craved.
USA lawmakers have raised concerns that traders in China are already skirting sanctions, but Beijing-based diplomats say that there is no evidence that China is abandoning its U.N. Security Council commitments. In the near term, China has repeatedly called for a freeze in large-scale U.S.
Just a week before his April visit to the demilitarised zone (DMZ) for his first summit with Moon, Kim declared an end to nuclear testing, effectively ending his "byungjin" twin strategy that pursues nuclear prowess alongside economic development. The North says it will not be unilaterally pressured into abandoning its nuclear programme.
China wants to see the Kim regime adopt Chinese-style economic reforms and has pressured South Korea to remove a US anti-missile system that it regards as threatening China's nuclear deterrent.