The tweet came after the Washington Post reported Tuesday that Pompeo made the trip over the first weekend of April.
The meeting was part of an effort to prepare for a historic meeting in the coming weeks between Trump and Kim, the paper said, quoting two people with direct knowledge of the trip.
The visit came shortly after Pompeo was nominated to be secretary of state, the paper said.
Speaking yesterday in Florida where he was hosting Prime Minister Shinzo Abe of Japan, Trump said he had given his blessing to discussions aimed at formally ending the Korean war. Setting the stage for a major breakthrough, he added that "a great chance to solve a world problem" was within reach on the Korean peninsula.
Trump had also confirmed that Washington and Pyongyang had been in contact at "very high levels" and that "five locations" were being considered for his meeting with Kim.