The three men had each been detained for over a year.
He said its policy was now "to concentrate all efforts into economic progress", but stressed that this had nothing to do with worldwide sanctions imposed on the country.
Mr Trump and his wife, Melania, boarded the plane for about five minutes before the men stepped out, shaking hands with the president and waving to waiting media and military personnel.
The Trump-Kim summit has no precedent in US-North Korean relations.
It was a bittersweet moment for the family of Otto Warmbier Wednesday night as three Korean-Americans were freed from captivity in North Korea Wednesday night and greeted by President Trump. Its foreign ministry said in a statement: "We hope this meeting will advance prospects for peace in the Korean Peninsula". "It's never been taken this far, there has never been a relationship like this".
The US President had earlier said on his Twitter it would be "quite a scene" when the detainees arrived in Washington.
The announcement of the highly-anticipated meeting comes hours after the return of three USA prisoners on home soil, after their release from North Korea. "We're not going to walk into an Iran deal", Trump added. "It would be a great thing if they are", he added.More news: Germany urges restraint in Middle East
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It was made offical earlier this week that three United States citizens that have been imprisoned in North Korea would be released.
"I really think we have a very good chance of doing something very meaningful", BBC quoted Trump as saying.
Trump and Jong Un are likely to discuss several topics, but the highlight of the meet is set to be the denuclearization of the Korean peninsula. More than a dozen abductees still remain missing, according to the Japanese government.
U.S. officials had looked at several sites other than Singapore for the historic meeting but each was seen as problematic.
It also follows historic talks between Kim Jong-un and South Korean President Moon Jae-in, which took place in April.
Last month the Korean leaders held their own historic meeting inside the Demilitarized Zone dividing the two sides.
Pompeo said he had a "good" conversation with North Koreans and did his best to convey the USA message to them.