Secretary of State Mike Pompeo departed Pyongyang Saturday after spending over 24 hours in the North Korean capital engaged in tense negotiations on the dismantling of the country’s nuclear weapons program.

In the highest-level discussions since President Donald Trump and North Korean leader Kim Jong Un’s historic summit in June, Pompeo did not meet with the head of the rogue nation state.

Instead he finished a second day of long talks with his counterpart, North Korea’s former spy chief Vice Chairman Kim Yong Chol, with commitments for more talks — both on the repatriation of American remains from the Korean War and the destruction of a missile engine testing facility.

“We had many hours of productive conversations,” Pompeo told reporters shortly before departing for Tokyo. “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.”

But in a statement issued after Pompeo had landed in Japan, North Korea said the talks were "regrettable" and accused Washington of trying to unilaterally pressure the country into abandoning its nukes. It also said the U.S. made "unilateral and gangster-like" demands, according to the Associated Press.

The statement by an unnamed North Korean Foreign Ministry spokesman accused the U.S. of betraying the spirit of the Trump-Kim summit.

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 denuclearization that had been firm."

Pompeo had earlier said both sides were still committed to “complete denuclearization,” as agreed to in a joint statement following June’s summit between Trump and Kim.

“No one walked away from that, they’re still equally committed, Chairman Kim is still committed,” Pompeo said from the tarmac in Pyongyang. “I had a chance to speak to President Trump this morning, I know my counterpart spoke with Chairman Kim during the course of our negotiations as well.”

But what “complete denuclearization” looks like is not yet clear, despite both sides agreeing to work towards it in the joint statement in Singapore.

The State Department has pushed back on reports that the U.S. is softening its position with North Korea, the spokesperson telling reporters Friday “nothing could be further from the truth.”

But previous demands by the U.S. for “complete, verifiable and irreversible denuclearization,” had seemingly made way for the phrase “final, fully verified denuclearization,” as used in a tweet by Pompeo, Friday.

"Our expectation is exactly what the President and Kim Jong Un agreed to and the Singapore Summit, and that's the denuclearization of North Korea,” Nauert said Saturday. “There's a lot of hard work that's left to be done. We never thought this was going to be easy, that's why the consultations continue."

Earlier Saturday, Vice Chairman Kim Yong Chol noted that “the world is paying close attention to our meeting.”

“We consider this very important too since it is the first senior level face-to-face meeting since the summit between our two leaders,” said Pompeo in response. “President Trump is committed to a brighter future for North Korea. So the work that we do the path toward complete denuclearization building a relationship between our two countries is vital for a brighter North Korea and the success that our two presidents demand of us.”

“Of course it is important,” Vice Chairman Kim told the U.S. Secretary. “There are things that I have to clarify.”

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

Pompeo had met with Kim Jong Un on both previous visits to the country but State Department Spokesperson Heather Nauert said there was no expectation of a meeting with the North Korean leader on this occasion.

The State Department did confirm that a letter had been delivered from Trump to Kim Jong Un. Nauert said that a copy of the Elton John CD Rocket Man had not been delivered, despite earlier reports.

The next round of discussions on the repatriation of Americans remains from the Korean War will take place around July 12 in the demilitarized zone at between the border of North and South Korea.

Trump announced last month that 200 sets of remains had already been returned to the U.S. but the administration later said that was not the case. The Department of Defense will take the lead in the mid-July discussions.

The North Koreans also confirmed the existence of a missile engine testing facility. Pompeo said negotiations on a path for the destruction of that facility will continue at the working level.

The U.S. and North Korea agreed to the establishment of working groups led on the U.S. side by Ambassador to the Philippines, Sung Kim. Kim, who previously held the position of Special Envoy for North Korea Policy, met with his North Korean counterparts Sunday in Panmunjom in the Demilitarized Zone between North and South Korea shortly before Pompeo’s trip.

Pompeo has now landed in Tokyo where he is expected to brief his Japanese and South Korean counterparts Sunday morning.