North Korea only invited a foreign press corps to witness the explosion of the nuclear test site in May.
Pompeo also visited Japan and South Korea, where he said Monday in Seoul that there had been "significant progress" toward an agreement for the North to give up its nuclear weapons. Chairman Kim said he's ready to allow them to come in.
It added that the two sides agreed on holding working negotiations for the second North Korean-U.S. summit as early as possible. "But we will get there".
After meetings in Pyongyang, Pompeo traveled to Seoul and briefed South Korean President Moon Jae-in on his meetings with Kim in the evening, without disclosing details to the media.
Pompeo also told reporters that a second summit between Trump and Kim was "pretty close".
Mr Pompeo and North Korean leader Kim Jong-un held talks over the weekend.
"These actions have affected the mutual trust between both sides, and has cast a shadow over the prospect of China-US relations, which completely go against the interest of our two peoples", Wang said.
Soon after the secretary of state left the country on his last visit, North Korea issued a statement lambasting his "gangster-like" demands.
Pompeo did not have a scheduled meeting with Chinese President Xi Jinping, a fact that a senior U.S. State Department official on the trip said was not unusual, even though top U.S. officials often meet Chinese heads of state on visits.
Later Kim said, "It's a very nice day that promises a good future" for both countries.
"Yeah, so we had a great, great visit this morning", Pompeo replied.
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Another planned trip by Pompeo to Pyongyang was scrapped after what Trump said was insufficient progress towards implementing the terms of the Singapore declaration.
Since Trump and Kim met in Singapore in June, US-North Korea relations have stalled.
On a more positive note, Wang said China was still willing to solve the trade dispute with the USA through negotiations, "but they must be conducted on an equal, honest and serious basis".
Pompeo, however, played down the differences. And so there'll be tactical places where we'll have debates and disagreements, that is a necessary component of getting to the best deliverable.
"Recently, as the USA side has been constantly escalating trade friction toward China, it has also adopted a series of actions on the Taiwan issue that harm China's rights, and has made groundless criticism of China's domestic and foreign policies", Wang said at the joint appearance with Pompeo.
Since the denuclearization effort got underway with a secret visit to the North by then-CIA chief Pompeo in April, there has been only limited progress, even since the June 12 Trump-Kim summit that many had hoped would jump-start the effort.
He said North Korean leader Kim Jong-un had agreed to allow global inspectors into the Punggye-ri nuclear test site that was dismantled in May. It has not taken any steps to halt nuclear weapons or missile development.
"We can't rule out the possibility that Washington. may move in the direction of partial easing of sanctions based on progress in denuclearisation", he said. USA officials have thus far said the penalties will remain in place until the North's denuclearization is fully verified.
Mr Moon spoke positively about Mr Pompeo's meeting with Mr Kim on Sunday, saying it set up conditions that make possible another summit between Mr Kim and United States President Donald Trump soon and will help the denuclearisation of the Korean peninsula.
It added that there was an agreement to hold working-level talks to arrange a second summit between Kim and Trump.
