“The US side came up only with its unilateral and gangster-like demand for denuclearisation,” the statement said, adding that the US call for “complete, verifiable, irreversible denuclearisation,” or CVID, runs “counter to the spirit of the Singapore summit”.

The “fastest way” to achieve a nuclear-free Korean peninsula was through a phased approach under which both sides took steps at the same time, KCNA said in a statement citing an unnamed foreign ministry spokesperson.

“We had anticipated the US side would come with a constructive idea, thinking we would take something in return,” the North Korean spokesperson said.

“But through the high-level talks, the trust between the DPRK and the United States is facing a dangerous situation where our resolve for denuclearisation, which has been firm and steadfast, may falter.”

That was in stark contrast to the comments of Pompeo, who said on Saturday he had made progress “on almost all of the central issues” in talks with North Korea, including on setting a timeline for its denuclearisation, but work remained to be done.

Speaking to reporters after a day-and-a-half of talks in Pyongyang, Pompeo said the two sides agreed to hold discussions on July 12 on the repatriation of remains of Americans killed in the 1950-53 Korean war, and also discussed “modalities” for the destruction of a missile engine testing facility.

Pompeo said he spent “a good deal of time” discussing a denuclearisation timeline and declaration of the North’s nuclear and missile facilities.

“I think we made progress in every element of our discussions,” he said, according to a pool report from US reporters who accompanied him to Pyongyang.

“These are complicated issues but we made progress on almost all of the central issues. Some places a great deal of progress, other places there’s still more work to be done.”

The negotiations followed US President Donald Trump’s summit with Kim Jong-un in Singapore last month, where the leaders signed a statement committing Pyongyang to “work towards complete denuclearisation of the Korean Peninsula”.

While hailed by Trump as ending the threat of nuclear war, the statement was short on clear commitments, and Pompeo has been tasked with negotiating a detailed plan in Pyongyang.

Professor Yang Moo-Jin at the University of North Korean Studies in Seoul said Pyongyang was “separating US bureaucrats from President Trump, expressing trust in him”.

“This is not to break the talks. The North is trying to get an upper hand in further negotiations,” he explained.

“North Korea expected Pompeo to bring a concrete proposal for security guarantee but it was disappointed as the US side reiterated the old demand that the North should denuclearise first before the US gives it anything in return.”

Asked about reports based on US intelligence assessments that North Korea had continued to develop its nuclear facilities even while engaging in dialogue, Pompeo said.

“We talked about what the North Koreans are continuing to do and how it’s the case that we can get our arms around achieving what Chairman Kim and President Trump both agreed to, which is the complete denuclearisation of North Korea,” he said.

“There is no – no one walked away from that, they’re still equally committed, Chairman Kim is … still committed.”

Saturday’s Pyongyang talks were held at a villa in an official compound close to the imposing mausoleum where North Korea’s former helmsmen Kim Il-sung and Kim Jong-il – the current leader’s grandfather and father – lie in state.

As the day began, Pompeo left the compound to go to a location where he could make a secure call to Trump away from potential surveillance, then returned to restart talks and they continued through a working lunch for almost six hours.

In opening remarks, Kim Yong-chol, a top North Korean party official and former spy agency chief, asked Pompeo if he had slept well on his first overnight stay in the country.

He then added: “But we did have very serious discussion on very important matters yesterday. So thinking about those discussions you might have not slept well last night.”

Pompeo responded that he had slept “just fine” but the exchange suggested tougher talks ahead.

Pompeo warned that “the path toward complete denuclearisation building a relationship between our two countries is vital for a brighter North Korea and the success that our two presidents demand of us”.

Kim replied: “Of course it is important. There are things that I have to clarify.”

“There are things that I have to clarify as well,” Pompeo responded.

Pompeo, who is on his third visit to Pyongyang, began the outreach when he was still Trump’s CIA director and remained the point man on negotiations after the process became public and he became secretary of state.

Many experts doubt Kim Jong-un’s willingness to “denuclearise” – a military deterrent to US intervention has long been a strategic goal of his isolated, autocratic regime – and few expect this to be a quick process, even if Washington wants results within a year.

Pompeo, accompanied by senior State Department and CIA officials, held several hours of talks on Friday evening and had a working dinner with Kim Yong-chol at which both were “cracking jokes” and “exchanging pleasantries,” according to Heather Nauert, the State Department spokeswoman.

They also, she said, agreed to set up working parties to pursue the “nitty gritty details” of how to make good on promises made in Singapore.

After the meeting, Pompeo headed to Tokyo to brief Washington’s Japanese and South Korean allies.

Additional reporting by Agence France-Presse and Bloomberg