Kim stood silently alongside, but the North Korean leader had earlier described their summit as a "a good prelude to peace".
The foreign minister posted a photo showing him with Kim at the place on Facebook.
On the eve of his big summit with Kim Jong Un, Trump on Monday piled on more tweets in his escalating trade war with Canada and sent out a top official to bash news reporting suggesting Trump's summit preparations could have been hindered by the lack of a top science adviser.
Indeed, the necessity of a last-minute meeting between the USA and North Korean summit negotiating teams led by Sung Kim, a former US special representative on North Korea policy and an experienced negotiator, and Choe Son-hui, North Korea's top diplomat for dealing with the United States, suggested that the agenda has yet to be fixed up.
Calling for phased and synchronous measures for denuclearization, requiring reciprocal actions by the United States, what Pyongyang also wants in return for its relinquishment of nuclear weapons is a security guarantee from Washington as well as the lifting of sanctions imposed by the United Nations and the Unites States. But North Korea's nuclear ambitions are the outcome, not the cause, of confrontation on the Korean Peninsula.
On the day before the meeting, weeks of preparation appeared to pick up in pace, with US and North Korean officials meeting throughout Monday at a Singapore hotel.
"The discussions between the United States and North Korea are ongoing and have moved more quickly than expected", the White House said in a statement.
"North Korea has previously confirmed to us its willingness to denuclearise and we are eager to see if those words prove honest", he said.
The topics on the table at the Kim-Trump summit have remained largely a mystery.
Even as he drew a tough line on lifting sanctions, Pompeo sought to ease North Korea's wariness about giving up a nuclear arsenal that provides a deterrent against foreign adversaries while also serving as a key point of national pride. Traffic was held up in the steamy midday sun and scores of bystanders were penned in by police when Trump went to meet Lee.
A group of North Korean security staff were seen coming back into the hotel with cardboard boxes, one with McDonald's takeaway.
Commenting for the first time on the summit, North Korea's state-run KCNA news agency earlier said the two sides would exchange "wide-ranging and profound views" to re-set relations. It heralded the summit as part of a "changed era". "Those two people will sit in a room tomorrow".
The summit is scheduled to begin at 9am, the White House said. USA officials have already established a contingency plan for a two-day summit should the two leaders agree to an immediate second-round of talks.
They had appeared cautious and serious when they first arrived for the summit at the Capella hotel on Singapore's Sentosa, a resort island with luxury hotels, a casino, man-made beaches and a Universal Studios theme park.
In a tweet on June 1, the scholar said, "This is the only way to advance if we are to avoid catastrophic failure of diplomacy or catastrophic success, ie, offering up too much to get a deal in Singapore".