(CNN) It began with great expectations, an eagerly-anticipated meeting with a reclusive leader, and a gift bag that included an Elton John CD .

It ended with a scuttled rendezvous, statements declaring disappointment and stalemate.

Secretary of State Mike Pompeo's overnight visit to Pyongyang last week failed to demonstrate any progress on denuclearization talks, leading one source with knowledge of the discussions to say the White House felt it went "as badly as it could have gone."

"The North Koreans were just messing around, not serious about moving forward," the source told CNN's Michelle Kosinski , adding that Pompeo had been promised a meeting with North Korea's Kim Jong Un, and so not getting that meeting sent a big message.

"By now it's abundantly clear that this approach is a dead end," said Adam Mount, a senior fellow and director of the Defense Posture Project at the Federation of American Scientists, where he covers US nuclear strategy, deterrence and North Korea.

"The White House has essentially tried to shoot for the moon and total disarmament, and it's clear that North Korea is not only not willing to do that, but sees very little reason to take steps in that direction," he told CNN.

A gulf does exist

Pompeo himself sought to mitigate any frustration that North Korea has still not publicly declared what it will or will not do in regards to its own nuclear weapons program.

Speaking to reporters Wednesday as he arrived in Brussels to attend the NATO summit with President Donald Trump, Pompeo said the road ahead was long and that it was on the North Koreans for change to occur.

"Look, this is a decades-long challenge, getting the North Koreans to make a fundamental strategic decision, which is that the nuclear weapons they possess today frankly present a threat to them and not security," Pompeo said.

"We have to get the entire country to understand that they have that strategically wrong. Chairman Kim told President Trump he understood that. I was there. I saw it," he said.

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While Pompeo declared the two sides were making progress, North Korea labeled the Americans' attitude as "regrettable" and said it differed from the spirit that buoyed both leaders when they met in Singapore on June 12.

"We expected the US to bring constructive measures to build confidence in accordance with the spirit of the US-NK summit," said a statement from state-run news agency KCNA. "However, the attitude of the US in the first high-level talks held on the 6th and 7th was indeed regrettable."

The comments showed "the gulf that does exist between the demands the United States and other nations are making and what North Korea is willing to do," said Australian Senator Penny Wong. She spoke to Australia's ABC radio from Washington, DC

"That is why it is so important that we agree that ... it is so important to continue the economic pressure through the sanctions regime," she said.

Maximum leverage is gone

But the ship of maximum leverage has sailed, argues Cheon Seong Whun, a former South Korean government official who worked in the defense and unification departments. It left, he says, the moment President Trump agreed to meet with Kim Jong Un without any preconditions.

"He lost leverage when he agreed to those talks," said Cheon, a visiting research fellow at the Asan Institute for Policy Studies. "That was a huge political mistake."

The theater behind the failed Pompeo visit was "a repeated strategy by the North Koreans," he said, dubbing it a repeat of US-DPRK talks during the 1990s

"The North Koreans have a very correct understanding of weak spots in Western politicians who try to make a deal with them. The politicians have to sound optimistic. Pompeo is not prepared to admit he made a mistake," Cheon told CNN.

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The White House has maintained that should North Korea fail to live up to its end of any bargain, sanctions will continue. But sanctions the Chinese government had previously enacted have loosened somewhat, says Adam Mount.

"Those other points of leverage are gone, the sanctions regime is gone, it won't come back. It will never be reconstituted at the level it once was, the Chinese are already easing enforcement and Trump has not maintained his relationship with China," Mount said.

"The maximum point in American leverage was before the president accepted the North Koreans' offer to meet. As soon as he did that, it's been downhill since."

Personal appeals to Trump

But one disappointing summit does not mean an end to diplomacy. The North Koreans demonstrated their determination to continue with the talks by appealing directly to Trump in the statement they issued that criticized his top diplomat.

"Should the headwind begin to blow, it would cause great disappointment not only to the international society aspiring after global peace and security, but also to both the DPRK and the U.S.," said the statement quoting a spokesman of the Ministry of the Foreign Affairs of the Democratic People's Republic of Korea on Saturday.

"If so, this will finally make each side seek another choice, and there is no guarantee this will not result in yet another tragedy. We still cherish our good faith in President Trump," the statement said.

Two days later, Trump returned the compliment.

"I have confidence that Kim Jong Un will honor the contract we signed &, even more importantly, our handshake," he tweeted the following Monday . "We agreed to the denuclearization of North Korea. China, on the other hand, may be exerting negative pressure on a deal because of our posture on Chinese Trade-Hope Not!"

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The question for the administration now is whether it shifts to a "more feasible approach" rather than continuing to demand all-out disarmament from North Korea without any economic concessions, says Adam Mount.

"This approach is clearly a dead end. There are no indications that North Korea is interested in returning to the world of 'fire and fury' ," Mount said, referring to the increasing tensions last year that prompted fears of military action from either side.

"The concern now is the president's reaction. Will he calculate that he stands to gain more domestically with returning to threats? Does he want to distract from domestic political or legal problems? All of those things could have volatile results."