The MFA also said Lee will meet President Trump separately on Monday.
Crude oil prices extended losses after retreating on Friday on concerns about surging USA output and falling demand in China.
"President Trump is hopeful, but he's also going into the summit with his eyes wide open", Pompeo told reporters.
Many analysts have suggested that the discussion about denuclearization means very different things to North Koreans than it does to American officials.
Cracks have also begun to appear in the "maximum pressure" campaign of economic sanctions against North Korea, even though Trump insists the USA won't loosen the screws until Pyongyang's nuclear program is dismantled.
Experts believe the North is close to being able to target the entire USA mainland with its nuclear-armed missiles, and while there's deep skepticism that Kim will quickly give up those hard-won nukes, there's also some hope that diplomacy can replace the animosity between the US and the North.
Special Operations Command (SOC) police officers patrol Orchard Road ahead of the Trump-Kim summit in Singapore, June 10, 2018.
At 10am, Choi strode into the Ritz Carlton with her team of four.
South Korea's KOSPI added 0.65 percent, and Japan's Nikkei climbed 0.55 percent.
Kim had people around the world reaching for the dictionary when he called Trump a "mentally deranged USA dotard", saying he would "tame" him with "fire". But any request for the USA to withdraw its 28,000 troops from South Korean bases would likely be rejected.
"When I woke up this morning, I saw the news in the newspaper that our respected marshal went to Singapore for the North Korea-US summit", said Han Il-gwang, a Pyongyang resident, displaying typical discretion. "Or we could have a failed summit that really takes us in the other direction".
Image Kim Yo Jong also enjoyed a walkabout in Singapore
But the spectacle was absorbing.
Trump continued to tweet angrily at Trudeau from Singapore, saying Monday: "Fair Trade is now to be called Fool Trade if it is not Reciprocal".
Curious onlookers wait for the departure of Donald Trump's motorcade from Singapore's presidential palace. The Capella hotel, set among luxury resorts, lush gardens, and across the road from a roller coaster, is the site of Tuesday's meeting. Singapore will be the furthest he is known to have traveled since taking over.
"The Beast": Donald Trump's armoured limo on the streets of Singapore.
In an apparent bid to lower soaring expectations fueled partly by himself, Trump has already signaled the possibility that it may take more than one meeting with Kim to seal an ultimate agreement. The fake negotiators remained out of sight as the real men hit the streets on Monday.
Lee said the cost was worthwhile.
"I do not know of a single USA official - and we talked to a lot of them - or Japanese official below the level of the president who thinks North Korea is going to denuclearize", Green said.
Press secretary Sarah Huckabee Sanders, US Ambassador to the Philippines Sung Kim and National Security Council senior director for Asia Matt Pottinger will attend the working lunch. Rodman went on Instagram to announce that he will be there to "give whatever support is needed" for Trump and Jong Un.
Ponsei University's John Delury told Singapore broadcaster AsiaNews that Trump was a disruptive force in traditional diplomacy but his tactics of a one-on-one meeting could work.
The North Korean autocrat's every move will be followed by 3,000 journalists up until he shakes hands with Mr Trump. The Worm has visited North Korea on multiple occasions and competed on Celebrity Apprentice in 2013.
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