His rosy outlook was nearly immediately rejected by North Korea's foreign ministry, which called the US attitude to the talks "regrettable" and accused the United States of making unilateral demands for denuclearization.
Pompeo also said the date could move by one or two days, . and the process will begin to develop in the days to come.
One mistake Richardson said the USA made in its negotiations with Pyongyang was "going first" and announcing the termination of some military exercises with South Korea.
The US Secretary of State Mike Pompeo met North Korean leaders in Pyongyang for two days of talks.
Washington's top diplomat embarked on an intense day of negotiations with his North Korean counterpart Saturday as he strives to nail down Pyongyang's commitment to nuclear disarmament.
"We were able to reaffirm our unwavering commitment to the continued strengthening of our trilateral cooperation toward the common goal of North Korea's complete, verifiable and irreversible dismantlement" of all nuclear weapons and missiles, Japanese Foreign Minister Taro Kono told a joint press conference.
"The North is trying to get an upper hand in further negotiations", Yang said.
Pompeo explained after the talks that teams from both countries would continue discussions as the US looks to see North Korea make good on its promises to denuclearize despite some resistance from the Kim regime. "These are complicated issues but we made progress on nearly all of the central issues". He stressed there was still more work to be done in other areas, much of which would be done by working groups that the two sides had set up to deal with specific issues.
Japan's Abe had praised Pompeo for his strong leadership on the issue after speaking with the Secretary of State Sunday.
Trump agreed to halt the exercises during his summit with Kim.
"They have gotten the U.S. to back off military exercises, back off using "CVID", back off the "Libya model" of rapid denuclearisation, back off on human rights, and to look the other way while China relaxes sanctions implementation".
Pompeo has bristled at the idea that the Singapore declaration amounted to an empty promise, saying repeatedly that Kim Jong Un had assured him in private conversations he was ready to give up his nuclear arms.
Pompeo said that North Korea, in the "many hours of talks" at a walled-off guesthouse outside downtown Pyongyang, reiterated its commitment to denuclearisation.
Now, as the afterglow of the Trump-Kim tete-a-tete wears off the prospect of any kind of easy North Korean solution is looking - unsurprisingly - like a mirage.
Leaked U.S. intelligence findings have concluded that North Korea does not intend to give up its nuclear program completely.
KCNA said Pyongyang had offered to discuss declaring a formal end to the 1950-53 Korean War to mark next month's anniversary of the armistice agreement.
The foreign ministers of Japan, the United States and South Korea on Sunday reaffirmed their unity in urging North Korea to denuclearize as promised, despite Pyongyang accusing Washington of making unilateral and "gangster-like" demands.
"Sanctions will remain in place until final, fully verified denuclearisation as agreed to by Chairman Kim (Jong Un) occurs", Pompeo said, adding that the United States would seek to smooth the path by providing security guarantees requested by Pyongyang. Nauert didn't immediately respond to a request for comment about North Korea's latest statement.