"We made significant progress. We will continue to make significant progress and we are further along in making that progress than any administration in an awfully long time," he told reporters before his departure to Beijing on Monday.
Pompeo met North Korean leader Kim Jong Un on Sunday in his fourth visit to Pyongyang to discuss measures to eliminate North's nuclear weapons.
Pompeo had two meetings with Kim on Sunday morning and afternoon, respectively, and a luncheon, which had lasted for a total of 5 1/2 hours, South Korea's presidential office spokesman Kim Eui-kyeom said in a Monday briefing.
He added that the meetings were private with only Kim Jong Un, his sister and close adviser Kim Yo Jong and an interpreter in attendance.
After meetings in Pyongyang, Pompeo traveled to Seoul and briefed South Korean President Moon Jae-in on his meetings with Kim in the evening, without disclosing details to the media.
He told Moon that North will invite an inspection team to confirm the dismantlement of its Punggye-ri nuclear test site, the spokesman said.
North Korea only invited a foreign press corps to witness the explosion of the nuclear test site in May. It raised questions whether the explosion would mean a compete disabling of the facility or a mere display.
Moon said Monday that Pompeo's visit to Pyongyang has created a mood for the second U.S.-North Korean summit to take place soon.
U.S. President Donald Trump tweeted Sunday that Pompeo "had a good meeting with Chairman Kim today in Pyongyang. Progress made on Singapore Summit Agreements! I look forward to seeing Chairman Kim again, in the near future."
Moon also said "efforts are underway to end the last Cold War in the world" and he expects Kim Jong Un will travel to Russia and Chinese President Xi Jinping will visit North Korea soon, in a cabinet meeting on Monday, according to the presidential office.
The North Korean leader could also have a summit with Japanese Prime Minister Shinzo Abe, he said.
"These things are creating a new regional order surrounding the Korean Peninsula. The new order will lead to a new system in the Northeast region," he said.