Trump administration press secretary Sarah Sanders wrote in a tweet.
Singapore has diplomatic ties with both the US and North Korea, and serves as a regional headquarters for many large US companies and US Navy vessels, which use Singapore's port facilities. However, North Korea still operates a small embassy in Singapore.
Rudy Giuliani says President Donald Trump's decision to cancel a summit brought North Korea's leader to "his hands and knees" to beg to reschedule the meeting.
Trump met last week at the White House with Kim Jong Un's top deputy, Kim Yong Chol, who delivered a letter from the North Korean leader.
US President Donald Trump's summit with North Korean leader Kim Jong-un will begin early on June 12 in Singapore, the White House has confirmed in its first announcement of a timetable for the closely-watched meeting.
A general view shows the Capella Hotel on the island of Sentosa in Singapore, June 6, 2018.
It is not clear exactly where Mr Trump and Mr Kim will stay at the hotel, but previous reports have suggested that the North Korean leader desires a suite and that the U.S. government may be willing to pay for it. The ex-Chicago Bulls and Los Angeles Lakers forward may even play a role in to play in the high stakes talks on North Korea's nuclear program, the New York Post reported.
Easing sanctions under a deal would likely need approval from Congress which has passed sanctions on North Korea.
The Singapore government has said police would make stricter checks of people.
Meanwhile, Kim Chang Son, who is often referred to as Kim's "butler" and led the pre-summit talks with the USA delegation in Singapore, flew from there to Beijing on Wednesday.
The summit is taking place following a rapid detente between Pyongyang and Seoul and Washington.