(CNN) For the first time since he chose to engage with the world, North Korea's Kim Jong Un has proposed a possible timeline for ridding the Korean peninsula of nuclear weapons: by the end of President US Donald Trump's first term in office.

But even as his message, conveyed by South Korean national security adviser Chung Eui-yong on Thursday, was delivered, the US was still waiting on meaningful and verifiable action from the formerly reclusive leader.

Chung was part of a South Korean delegation that crossed the border into North Korea on Wednesday and met with Kim. There was at least one demonstrable outcome from this trip: a date for the next inter-Korean summit between Kim and South Korean President Moon Jae-in, September 18 to 20 in Pyongyang.

It's an auspicious time for the Hermit Kingdom. On Sunday it will mark the 70th anniversary of the founding of the Democratic People's Republic of Korea.

Talks between Washington and Pyongyang have stalled. President Trump canceled Secretary of State Mike Pompeo's planned trip last month, citing little evidence that North Korea had come through on any of its commitments to denuclearize.

The task of bringing the two sides back together will again fall to President Moon, who has served as an intermediary, and who has made peace with the North his greatest mission as South Korea's leader.

Time for Moon to make a play

Moon will be coming into his summit with Kim ready to make a play, said Duyeon Kim, an adjunct senior fellow at the Center for a New American Security.

"It's possible Moon will try to broker a trade off between Washington and Pyongyang that will involve a declaration that the war is over, and so the nuclear negotiations can move forward," she told CNN.

"The bottom line is that Pyongyang would have to take a genuine denuclearization step, not a symbolic one, that is convincing and acceptable enough for Washington to be able to continue its negotiations in a give and take fashion."

She suggests that in exchange for a declaration of an end to the Korean War, Kim immediately respond with an inventory of North Korea's arsenal -- something Secretary of State Mike Pompeo had tried to obtain when he visited Pyongyang in July, Reuters reported at the time.

North Korea's reluctance to do anything outside of its own timetable and comfort has frustrated negotiators.

Right now, argues David Maxwell, a retired US Army Special Forces colonel who served five tours on the Korean Peninsula, the White House has made a ton of concessions to Pyongyang and not gotten any credit for them.

"We suspended the military exercises and that's a significant blow to military readiness, and the North has not reciprocated," he told CNN. "It's like with any blackmailer, you pay the ransom and they just want more and President Trump has got no credit for that because it's done, and this is a lesson we have to learn."

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Kim insisted the reverse was actually the case during his meetings with South Korean officials, said Chung, that North Korea has already taken steps, including dismantling a missile test site and a missile engine facility.

"If reciprocation is shown for North Korea's preemptive measures that have already been completed, he (Kim) strongly expressed his will that more active measures for North Korea's denuclearization can be taken," Chung said.

Symbolic but meaningless denuclearization

Speaking at a conference of intelligence officials this week, Dan Coats, the Director of National Intelligence, said that despite a pause in weapons testing it wasn't possible to know what steps North Korea has taken to denuclearize beyond the destruction of a nuclear test site that some experts believed was no longer operational anyway.

"... Absent mechanisms for on the ground verification for inspectors, we cannot confirm that North Korea has taken any other denuclearization steps at this time," Coats said Tuesday. "This North Korean commitment, and I put 'commitment' in parantheses -- to denuclearize presents a huge and critical challenge to our intelligence community -- complete and accurate collection and analyses is essential to achieve our long standing goals."

Coats' comments exemplify the differences between the two nations regarding what each side considers to be active steps on the path to denuclearization. The US doesn't hold that many of the moves made by North Korea so far -- including the repatriation of fallen US troops , or the release of American detainees -- are connected with the nuclear issue.

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But to Kim Jong Un, it is all part of a demonstration of his "good faith" in dealing with the US.

Kim "reaffirmed his determination to completely denuclearize" the peninsula, South Korea's Chung insisted upon his return to Seoul on Thursday.

"Chairman Kim," he said, "expressed frustration over the doubt shown by some parts of the international society about his will."

"North Korea has been preemptively carrying out measures needed for denuclearization, and Kim said he would appreciate that such good faith is accepted with good faith," Chung said.

Who goes first?

"The biggest thing is that it is a process issue and a timing issue and who goes first," said Maxwell, a Senior Fellow at the Foundation for Defense of Democracies. "The North Koreans are locked into a declaration to the end of the war, then end of sanctions, then denuclearization and dismantlement of North Korea's nuclear weapons."

"Of course, we want denuclearization first, but we might be able to accept substantive progress towards dismantlement and then a gradual reduction of sanctions and hopefully a peace treaty," Maxwell told CNN. "When I look at the North, I just don't see them changing. I don't see that they've changed."

Bruce Bechtol, a professor of political science at Angelo State University, who has authored several books on North Korea, said that much depends on Moon regarding what happens next.

"Moon is a really enthusiastic guy for engagement with the North at all costs, with no cost to the North at least thus far," he told CNN. "That's why we see all this stuff about them moving forward no matter what, even if the North Koreans violated the sanctions."

"I believe that no matter how the summit turns out, Moon will act as if this is a groundbreaking move. That will be how he portrays it to the South Korean people. North Korea has no plans to dismantle," Bechtol said.

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Last month a confidential United Nations report accused North Korea of continuing to develop nuclear and missile programs in violation of international sanctions. It also said North Korea continues to defy an arms embargo and financial sanctions -- which it calls "some of the most poorly implemented and actively evaded measures of the sanctions regime."

An end to the war, but not really

The declaration sought by Pyongyang ostensibly is a symbolic one. There is still an armistice in place and such a declaration could not replace it, said Duyeon Kim.

"There's going to have to be a crystal clear agreement with Pyongyang and an understanding with Moscow and Beijing as well, that it doesn't alter the armistice. There can be no ambiguity for international lawyers," she told CNN.

"Or else Pyongyang, Beijing and Moscow could aim straight for the armistice to be abolished, and eventually get the UN command and the US troops out of the peninsula. In that scenarios, nuclear negotiations could be held hostage to peace negotiations," she said.

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But giving Pyongyang another thing it wants before it concedes anything to the US continues to play into Kim Jong Un's hands. For the North Korean leader, complete denuclearization of the peninsula includes the US troops in the South as well.

If Kim stalls again, even after Moon's overtures, the next move will fall to Trump, already irritated by the lack of action from the North.

"And if North Korea hasn't made any credible steps then the concern is that Trump might consider military options even before considering long term containment and deterrence," said Duyeon Kim. "There's no telling what Trump will decide to do."