The delegation, which includes White House Deputy Chief of Staff Joseph Hagin and deputy National Security Adviser Mira Ricardel, was being dispatched after Trump said on Tuesday there was a "substantial chance" the summit would be called off amid concerns Pyongyang is not prepared to give up its nuclear arsenal.
The hearing was contentious at times, particularly when Democratic Representative Greg Meeks confronted Pompeo about his aggressive questioning of former secretary of state Hillary Clinton when he was a congressman during Republican-led hearings about the fatal 2012 attack on USA diplomats in Benghazi.
North Korea gathered up some 30 foreign journalists on Wednesday morning for a trip to a mountain where it carried out a massive nuclear test in September - but this time, North Korea will be closing the site down.
Trump told reporters at the White House during his meeting with Moon Jae-in that "if it doesn't happen, maybe it will happen later".
"We're optimistic that we can achieve an outcome that would be great for the world", Pompeo said.
Yet ahead of a bilateral meeting with South Korean President Moon Jae-in-who met Kim for the first time on April 27-Trump cast doubt over the prospect of the summit happening at all. "We still look forward to the meeting between the USA and North Korean leaders proceeding smoothly and achieving positive results".
"The North Koreans have good reason to be alarmed by what Trump meant as assurances but what came across as a threat to "decimate" their country if it didn't surrender its nuclear arms".
Kim's paranoia about losing power is believed to have played a role in the assassination of his older half-brother Kim Jong Nam early a year ago in a Malaysian airport.
Why does the Singapore summit matter so much?
China said both the United States and North Korea were still making preparations for the summit, and Beijing hoped both sides can "clear away distractions".
It would be historic as no sitting United States president has ever met a North Korean leader.
"I can tell you what it is that President Trump has instructed me to do with respect to how we are going to proceed against North Korea", Pompeo said.
Pompeo said Trump would be leading the talks but declined to discuss how many people, or who, would be on the summit team.
However, Pyongyang's professed commitment to "denuclearisation" is likely to differ from Washington's demand for "comprehensive, verifiable and irreversible" nuclear disarmament.