Trump was received by Lee at the presidential palace Istana, where they were expected to discuss summit preparations, US' tariff threats.
Singapore: US President Donald Trump on June 11 met Singapore Prime Minister Lee Hsien Loong, just a day before his historic summit with North Korean leader Kim Jong Un.
Trump was received by Lee at the presidential palace Istana, where they were expected to discuss everything from the summit preparations to the US' tariff threats.
Read: Trump to hold bilateral meetings with Singapore PM ahead of US-N Korea summit
The US president was accompanied by Secretary of State Mike Pompeo, National Security Adviser John Bolton, White House Press Secretary Sarah Sanders and White House Chief of Staff John Kelly.
The meeting was Trump's only scheduled public event on Monday.
Lee also hosted a working lunch for Trump and his delegation. At the lunch, Trump expressed optimism for Tuesday's meeting with Kim and also thanked his Singapore hosts for their hospitality.
"We have a very interesting meeting, in particular, tomorrow, and I think things can work out very nicely," he said. "But we appreciate your hospitality and professionalism and your friendship."
Earlier, Trump tweeted it was "great to be in Singapore, excitement is in the air".
On June 11, Sung Kim, a former US ambassador to South Korea and former nuclear negotiator with the North, will lead a US delegation for a working group with a North Korean delegation at the Ritz Carlton hotel, Sanders said.
"We are also planning a briefing by senior administration officials in the filing centre at the JW Marriott tentatively scheduled for 5 pm local time," she said in the briefing note issued in Washington on Sunday.
During the flight, the president spent time meeting with his staff, reading materials, and preparing for his meetings in Singapore.
Chairman Kim on June 10 held a meeting with Prime Minister Lee. He thanked Singapore's organisation of the summit as if it was "their own family affair".
The two leaders discussed bilateral relations as well as the summit and the recent positive developments on the Korean peninsula. Lee complimented the bold and admirable decision by Kim and Trump to come together for the Summit.
Prime Minister Lee wished Kim a success for the summit and expressed hope that the US-North Korea meeting will advance the prospects for peace and stability in the Korean peninsula and the larger region.
Singapore is one of the few countries that have diplomatic relations with both the US and North Korea.
Trump and Kim are set to meet on Tuesday, June 12 at the Capella Hotel on Sentosa for talks which could see North Korea dismantle its nuclear arsenal in return for economic help and security guarantees.
The summit will be the first meeting between Trump and Kim and mark a turnaround of relations between the two leaders after a long-running exchange of furious threats and insults. The two leaders have had an extraordinary up-and-down relationship over the past 18 months.
Some 2,500 journalists are reporting on the event, which is costing Singapore government about SGD 20 million.