Mike Pompeo hit back at North Korean accusations of "gangster-like" behaviour on Sunday and said sanctions on Pyongyang would only be lifted with "final" denuclearisation.
Speaking in Tokyo after two days of intense discussions in Pyongyang, the US Secretary of State insisted the talks were making progress and were being conducted in "good faith."
In stark contrast, Pyongyang's take was overwhelmingly negative, with the North warning that the future of the peace process was being jeopardised by overbearing US demands for its unilateral nuclear disarmament.
In Tokyo, Mr Pompeo briefed his Japanese and South Korean counterparts on the talks, and sought to reassure them that the dialogue with North Korea would continue.
His trip to Pyongyang had been aimed at fleshing out denuclearisation commitments made during last month's historic summit between President Donald Trump and North Korean leader Kim Jong-un.
Rocket man: How Kim Jong-un emerged from his father's shadow to silence the doubters
North Korea has long trumpeted a denuclearisation goal, but one that it sees as a lengthy process of undefined multilateral disarmament on the entire Korean peninsula, rather than a unilateral dismantlement of its nuclear arsenal.
Mr Pompeo said his efforts to push the North on disarmament had the backing of the entire international community.
"If those requests were gangster-like, the world is a gangster, because there was a unanimous decision at the UN Security Council about what needs to be achieved," he said.
While insisting again that the talks were moving forwards, he stressed that nothing had happened to merit a relaxation of the tough sanctions imposed on the North over its nuclear missile programme.
"Sanctions will remain in place until final, fully verified denuclearisation as agreed to by Chairman Kim (Jong Un) occurs," Mr Pompeo said, adding that the US would seek to smooth the path by providing security guarantees requested by Pyongyang.
In practical terms, Mr Pompeo mentioned only that officials from both sides would meet on July 12 to discuss the repatriation of the remains of some US soldiers killed during the 1950-1953 Korean War.
America's top diplomat had attempted to receive specific commitments from the North Koreans on denuclearisation and the repatriation of the remains of American soldiers killed during the Korean War.
However, in a statement reported by the North's official news agency, a spokesman for the Foreign Ministry said: "We had expected that the US side would offer constructive measures that would help build trust based on the spirit of the leaders' summit ... we were also thinking about providing reciprocal measures".
"However, the attitude and stance the United States showed in the first high-level meeting (between the countries) was no doubt regrettable," the spokesman said. "Our expectations and hopes were so naive it could be called foolish," he added.
Mr Pompeo had admitted that "there's still more work to be done", much of which would be done by working groups that the two sides have set up to deal with specific issues.
The North provided a much harsher assessment of the talks, saying that the United States betrayed the spirit of last month's summit between President Donald Trump and Kim by making "one-sided and gangster-like" demands on "CVID," or the complete, verifiable and irreversible denuclearisation of North Korea.
It said the outcome of the follow-up talks was "very concerning" because it has led to a "dangerous phase that might rattle our willingness for denuclearisation that had been firm."
In the days following his historic June 12 summit with Kim in Singapore, Mr Trump claimed the return of the remains and the destruction of the missile facility had been completed or were in progress. It later emerged further talks were needed on both issues.
The trip was Mr Pompeo's third to Pyongyang since April and his first since the summit.
North Korea’s fiery relationship with the US
Unlike his previous visits, which have been one-day affairs during which he has met with Kim Jong-un, Mr Pompeo spent the night at a government guesthouse in Pyongyang and did not see the North Korean leader, although US officials had suggested such a meeting was expected.
State Department spokeswoman Heather Nauert said no meeting with Kim had been planned.
As they began their talks on Saturday, Kim Yong-chol alluded to the fact that Mr Pompeo and his delegation had stayed overnight in Pyongyang.
"We did have very serious discussions on very important matters yesterday," Mr Kim told him. "So, thinking about those discussions you might have not slept well last night."
Mr Pompeo, who spoke with Mr Trump, national security adviser John Bolton and White House chief of staff John Kelly by secure phone before starting Saturday's session, replied that he "slept just fine."
He added that the Trump administration was committed to reaching a deal under which North Korea would denuclearise and realise economic benefits in return.
Mr Kim later said "there are things that I have to clarify" to which Mr Pompeo responded that "there are things that I have to clarify as well."
There was no immediate explanation of what issues needed to be clarified, but the two sides have been struggling to specify what exactly "denuclearisation" would entail and how it could be verified to the satisfaction of the United States.
Mr Pompeo and Mr Kim met for nearly three hours on Friday and then had dinner amid growing scepticism over how serious the North Korean leader is about giving up his nuclear arsenal and translating the upbeat rhetoric following his summit with Mr Trump into concrete action.