(CNN) The top US military commander on the Korean peninsula said Friday that even as the United States and North Korea work on easing tensions and working toward denuclearization, diplomacy between the two nations was operating in an environment "void of trust."

Speaking by teleconference to the Aspen Security Forum, Gen. Vincent Brooks said the peninsula had "gone now 235 days without a provocation." On November 28 last year, North Korea tested an intercontinental ballistic missile that it claimed could reach the US mainland. Since then, North Korean leader Kim Jong Un said his regime had done all the testing it needed to do, and dismantled at least one test site.

During his summit with President Donald Trump in June, he reportedly promised the US leader that he would also take apart another site , but it is not clear whether that has occurred.

"Our challenge now candidly is to continue to make progress but to make that progress in an environment that is essentially void of trust, and without trust we'll find it difficult to move forward," said Brooks, the commander of US forces in Korea, who is also in charge of the United Nations command and the combined South Korea-US forces command.

"So building that trust while that pressure continues and while the efforts for diplomacy continue is the order of the day. In many ways the lack of trust is the enemy we now have to defeat," he said.

'The world is a gangster'

The most recent diplomatic foray by US Secretary of State Mike Pompeo to Pyongyang earlier in July was not particularly successful.

Pompeo, who was expected to see Kim Jong Un during the visit, left North Korea without meeting the dictator. His plane had barely taken off from Pyongyang international airport when North Korean state media announced the regime's displeasure with the way the talks had gone.

"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.

"However, the attitude of the US in the first high-level talks held on the 6th and 7th were indeed regrettable."

The United States displayed a "gangster-mindset" during the talks, the North Koreans said.

Pompeo pushed back soon after.

"If those requests were gangster-like, the world is a gangster," he said, adding that the two sides "had detailed, substantive conversations about the next steps toward a fully verified and complete denuclearization."

"No one's been closer to that than I have," he told Fox News on Thursday. "Everyone else is simply speculating. I've been there."

He added that the North Koreans "have consistently reaffirmed their commitment" to the deal agreed to by Trump and Kim in Singapore.

"No one was in any confusion that this was going to happen in hours or days," he said, adding that discussions are continuing and the country has a "bright future."

Demonstrable action 'or we cannot be satisfied'

Gen. Brooks argued that the "maximum pressure" campaign the United States instituted last year, pushing punishing sanctions on the Kim regime, coupled with intensified military pressure, had contributed to compelling North Korea to engage with the international community.

With Kim's noted promise to denuclearize the peninsula must, however, also come viable action that backs up the promise, Brooks said.

"There has to be demonstrable action in that direction or we cannot be satisfied and we probably can't be friends and we probably won't be at peace," Brooks told the audience. "So we have to see something moving in both directions in order to get us there."

From his perch in South Korea, Brooks said he has seen some changes in the pattern of behavior and training of North Korea's million-plus army, the majority of which are positioned between Pyongyang and Seoul.

He said he has seen some reduction in training readiness from North Korean troops.

"They have to alternate their training with harvesting and planting. We've seen some changes in terms of how much time they're spending in the field. Some of that might be attributed to fuel shortages; some of that might be because of the renewed engagement," he said.

He also noted that in terms of what North Korea has promised to do regarding the denuclearization process, nothing has actually changed on the ground.

"Let's say their production capability is still intact," he said. "We haven't seen a complete shutdown of production. We have not seen removal of fuel rods. There still steps that must be taken on the road to denuclearization."

Transfer of human remains

Brooks said at least some remains of Americans killed during the Korean War would be brought back to the United States.

"We are confident we'll succeed in transferring some of the remains. Not all of them, but some of them," he said. "The pain of those families is as acute today as it was then."

At least one US official told CNN on July 17 that North Korea would return the first set of possible US service member remains on July 27 , the anniversary of the signing of the armistice that signaled the end of the Korean war.

On that day in 1953, Chinese, North Korean and UN forces signed the armistice, which also established the parameters of the demilitarized zone that separates North and South Korea.

On June 24, US forces in South Korea sent 100 wooden transport cases to the Demilitarized Zone to prepare to receive the remains.

The date of their return has been unclear. On July 12, North Korean officials did not turn up to a meeting with US officials at the DMZ where they were set to discuss the repatriation of the remains.

Brooks downplayed possible posturing by North Korea as the discussions between the two countries continue, saying that diplomacy takes time. This includes, he said, reports of North Korea stepping up its nuclear production activity

"We don't overreact to things like that," he said. "If those things are true, what does it mean to us as we go forward? It could mean several things. We know what our end point is and we know what they've agreed to, so let's keep our eye on that and not get distracted."