After progress between Pyongyang and Seoul, analysts highlight difficulties ahead for US to achieve denuclearisation.

One year ago, US President Donald Trump mocked North Korean leader Kim Jong-un as “rocket man” and threatened to “totally destroy” his country. This week, after positive inter-Korean talks in Pyongyang, Trump tweeted that progress there was “very exciting!”.

It is remarkable how, in just 12 months, relations have swung around from threats of atomic Armageddon to red carpets, warm embraces and arms reduction talks – especially given the dogged personalities of those involved.

But analysts told Al Jazeera while South Korean President Moon Jae-in’s three-day trip to North Korea yielded dividends, stark divisions remain between the main players, and the peace process could yet unravel, as happened in previous efforts.

“The progress suggests that Kim is serious about reducing inter-Korean tensions and moving closer to peaceful coexistence. Crucially, Moon got enough cooperation from Kim on denuclearisation to add some momentum to US-North Korea talks,” Scott Snyder, author of South Korea at the Crossroads, told Al Jazeera.

“But there are still big questions, including the relationship between inter-Korean economic cooperation, tension-reduction and denuclearisation, as well as Pyongyang’s final asking price for the measures proposed.”

North-South talks

The mood was upbeat throughout Moon’s visit across the 38th parallel (the line that demarcates North and South Korea) – two leaders of a divided peninsula hugging each other, brass bands, saluting children and crowds of North Koreans shouting “reunification of the fatherland!”.

The high point, quite literally, was a photo opportunity of Kim, Moon and their wives atop Mount Paektu, in front of the sacred volcano’s glistening crater lake on Thursday, after the leaders had inked deals on transport, trade and curtailing military activity.

Their joint declaration outlined new road and rail links and the reopening of Kaesong industrial complex shut down in 2016 and Mt Geumgang Tourism Project in a bid to promote trade and economic ties.

Kim said he would visit Seoul soon, which would be a first for a North Korean leader. As well as making it easier for Korean families separated by the war to reunite, they announced plans to jointly host the 2032 Summer Olympics.

They also agreed to work to “prevent accidental military clashes” and to withdraw 11 guard posts from the Demilitarized Zone (DMZ) that has separated the two countries since the 1950-53 war ended with an armistice but not a peace treaty.

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One of Moon’s other goals was to revive denuclearisation talks between the US and North Korea, which gained traction at a Trump-Kim summit in Singapore in June but have since floundered amid fears that Pyongyang continues to stockpile nuclear weapons.

Moon secured a pledge from Pyongyang that it would allow foreign observers to watch as a missile engine test site at Tongchang-ri is permanently dismantled, and another to shutter the Yongbyon nuclear complex if the US undertook unspecified reciprocal steps.

It is unclear what “corresponding measures” Kim had in mind, though they likely relate to a peace treaty to formally end the decades-old war, relief from crippling sanctions and the 28,500 American troops stationed in South Korea to deter North Korean attacks.

Despite this caveat, there was enough progress to revive the fledgling talks between Washington and Pyongyang. Trump was upbeat. His Secretary of State, Mike Pompeo, said the US “is prepared to engage immediately in negotiations to transform” the relationship.

Pompeo also set a specific deadline on North Korean denuclearisation, giving a January 2021 end date. He invited North Korean Foreign Minister Ri Yong Ho to meet in New York next week on the sidelines of the annual UN General Assembly meeting of world leaders.

‘Periphery concessions’

All eyes are now on the UN, where Trump referred to Kim as a “rocket man” a year ago. In New York, Moon is set to debrief Trump on the summit, and Pyongyang could yet deploy a senior envoy. Pompeo will also chair a Security Council meeting on North Korea on September 27.

Upon returning to Seoul on Thursday, Moon spoke of a “second summit” between Trump and Kim to “take place in the near future” in comments that were widely viewed as a signal that the ball is now in Washington’s court.

Trump’s enthusiasm for the talks is not matched by some officials lower down in his administration, many of whom have watched past initiatives fail and doubt Pyongyang has any intention of bargaining away its hard-won nuclear deterrent.

“There is nothing the North has offered so far that would constitute irreversible movement toward denuclearisation, however you define that, by January 2021 or any other time,” a US intelligence official told Reuters, on condition of anonymity.

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Others point to Kim’s negotiation prowess – driving a wedge between Washington and Seoul, and nudging Trump to make concessions before he dismantles nuclear-tipped missiles that are feared by the US and its allies, South Korea and Japan.

Larry Niksch, an expert with the Library of Congress’s Congressional Research Service, told Al Jazeera that Moon had only extracted “periphery concessions” from Kim and that it remained unlikely that Pyongyang would scrap its nuclear programme.

“What worries me most is that we see no progress on the verification issue, which means getting an inspection organisation implanted into North Korea with broad-ranging powers and authorities to inspect sites without being interfered with in any way,” said Niksch.

Wendy Sherman, a top official in the State Department under the Obama administration, said Trump was undercutting his own arms control talks by levying tariffs on imports from China, one of the few countries with leverage over Pyongyang.

In Sherman’s analysis, the US views denuclearisation as Kim scrapping his nukes, while Pyongyang envisages American forces leaving the peninsula. Likewise, both Pyongyang and Seoul call for reunification, but each wants a united Korea on its own terms.

“At some point … efforts are going to come to a resounding – I’m sad to say – crash,” she said.