(CNN) North Korea slammed what it called the United States' "gangster-like mindset" in denuclearization talks just hours after US Secretary of State Mike Pompeo described the high-level negotiations as "productive" and insisted progress was made.

"We had many hours of productive conversations," Pompeo told reporters Saturday in Pyongyang before boarding a flight to Tokyo. "These are complicated issues, but we've made progress on almost all the central issues. Some places, a great deal of progress. Other places, there's still more work to be done."

North Korea, however, poured cold water on the talks, saying the "attitude" of the US was "regrettable" and not in the spirit of the June 12 summit in Singapore between President Donald Trump and North Korean leader Kim Jong Un.

"We expected the US to bring constructive measures to build confidence in accordance with the spirit of the US-NK Summit," the statement carried by state-run news agency KCNA said, according to a CNN translation of the Korean version of the statement. "However, the attitude of the US in the first high-level talks held on the 6th and 7th were indeed regrettable."

The statement added, according to an English-language version of the statement released by KCNA: "The US is fatally mistaken if it went to the extent of regarding that the (Democratic People's Republic of Korea) would be compelled to accept, out of its patience, the demands reflecting its gangster-like mindset."

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