On Monday evening, Kim's first stop was a waterfront park with futuristic installations, Gardens by the Bay, which boasts the largest glass greenhouse and tallest indoor waterfall in the world.
In one video clip, Mr Kim waves to crowds as he enters Marina Bay Sands Hotel surrounded by a team of robotic body guards.
Mr Trump had earlier tweeted about the "excitement in the air".
The two leaders have had an extraordinary up-and-down relationship over the past 18 months.
Sanctions will remain until North Korea completely and verifiably eliminates its weapons of mass destruction programs, added Pompeo.
Historic meetings between the USA and North Korea have advanced so rapidly that Donald Trump will leave Singapore earlier than expected. Others complained about the traffic jams in downtown Singapore.
Kim remained ensconced in the heavily guarded St. Regis Hotel, where he is staying. Sung Kim held an initial round of meetings with the North earlier Monday.
In Singapore, the island city-state playing host to the summit, the sense of anticipation was palpable, with people lining spotless streets Monday waving cellphones as Trump headed to meet with Singapore's Prime Minister Lee Hsien Loong.
He also seemed to be optimistic about the summit, saying: 'We've got a very interesting meeting in particular tomorrow, and I think things can work out very nicely'.
Both sides were finalizing preparations for the unprecedented summit, which was to kick off at 9 a.m. Tuesday with a handshake between Trump and Kim, an image sure to be devoured around the world.
Traffic was held up in the steamy midday sun and scores of bystanders were penned in by police when Mr Trump went to meet Mr Lee.
Accompanying Kim Jong Un on the night-time sightseeing tour was his security detail as well as his sister and close adviser Kim Yo Jong, who arrived to Singapore on Sunday on a separate plane from her brother, and former foreign minister and ruling party high-ranking official Ri Su Yong, South Korean news agency Yonhapreported. Their hotels, less than a kilometre (mile) apart, are cordoned off with heavy security.
She emerged as an influential figure in Pyongyang's opaque leadership in February, when she led a North Korean delegation to the Winter Olympics in South Korea.
"The ultimate objective we seek from diplomacy with North Korea has not changed - the complete, verifiable and irreversible de-nuclearization of the Korea peninsula is only outcome that the United States will accept", declared Pompeo.
Even so, the summit continues to be a highly sensitive topic in North Korea and it is hard - even more so than usual - to get people to express their opinions about it. "This is not the fault of either Trump or Kim, but rather a reflection that intractable, decades-long strategic challenges rarely-if ever-get resolved in single encounters", Haas writes. "The process could be doomed before it begins".
"I'm hopeful that he's right", said Perry, who negotiated with North Korea during Bill Clinton's presidency in the 1990s. "We can go fast, we can go slowly", Trump said.
From there, the two leaders will head to a one-on-one meeting accompanied only by translators, then to a second bilateral meeting with more participants, and finally to a working lunch. He described it as a "get to know you plus" meeting.
President Donald Trump and North Korea's Kim Jong Un spent Monday huddling with advisers in luxury Singapore hotels less than half a mile apart, readying for a nuclear summit that could define the fate of millions, and their own political futures. Enemies since the Korean War, the leaders of North Korea and the United States have never met previously - or even spoken on the phone.
But he has since lowered expectations, backing away from an original demand for North Korea's swift denuclearisation.
Kim Agrees to Send Remains of US Soldiers Home
In the face of the North's constant protest, the allies' militaries have defended the exercises as purely defensive in nature. The drills - often called "war games" - are held in South Korea with local forces and United States soldiers stationed there.