Kim Jong Un’s long, slow train journey from Pyongyang to Beijing was an attempt for the dictator and his host to gain leverage ahead of the North Korean leader’s summit with President Donald Trump, according to experts.

Kim’s trip to meet with the country’s oldest and only real ally has been shrouded in mystery. Little is known about what was discussed between the two leaders other than an official statement published through China’s state-run media.

His departure from China also came one day before the date for the first inter-Korean summit in 11 years was announced. Kim will meet with South Korean President Moon Jae-in on April 27, officials confirmed Thursday.

“It seems China was not comfortable with the idea of Kim meeting with Moon and Trump before having ever met with Xi,” said Paul Haenle, who served as China affairs director for the National Security Council under George W. Bush and Barack Obama.

From a North Korean perspective, it may also have made sense to shore up their sometimes fractious relationship with Beijing ahead of any U.S. meeting, Haenle added.

“Kim may have felt he had secured some leverage against Xi having independently secured summits with Trump and Moon," said Haenle, who is now director of the Carnegie–Tsinghua Center for Global Policy in Beijing. "He’ll now feel more confident knowing where things stand with Beijing heading into those same meetings.”

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Kim's visit comes just weeks after China's rubber-stamp parliament voted to abolish term limits, effectively allowing President Xi Jinping to rule the superpower indefinitely. It also comes amid heightened tensions between Beijing and Washington over trade, with Trump announcing new tariffs on imported steel and aluminium from China earlier this month.

Cristina Varriale, a research analyst specializing in proliferation and nuclear policy at the London-based Royal United Services Institute, told NBC News this week's visit could help ensure China plays a much more active role in any denuclearization agreement.

“With the recent engagement between North and South Korea and the South Koreans going to the U.S. it started to look very much like a tri-lateral initiative between those three countries," she said. "By pulling China back into it, North Korea are balancing it out again and having their patron back on their side as part of this process.”

After Kim’s meeting with Xi, President Trump tweeted that he was hopeful denuclearization of the Korean peninsula would finally take place, adding “there is a good chance that Kim Jong Un will do what is right for his people and for humanity.”

For years and through many administrations, everyone said that peace and the denuclearization of the Korean Peninsula was not even a small possibility. Now there is a good chance that Kim Jong Un will do what is right for his people and for humanity. Look forward to our meeting! — Donald J. Trump (@realDonaldTrump) March 28, 2018

Trump also noted that Xi had kept him abreast of his discussions with Kim.

Received message last night from XI JINPING of China that his meeting with KIM JONG UN went very well and that KIM looks forward to his meeting with me. In the meantime, and unfortunately, maximum sanctions and pressure must be maintained at all cost! — Donald J. Trump (@realDonaldTrump) March 28, 2018

But is there a real prospect of denuclearization on the peninsula? Varriale isn’t convinced. “There is still a really, really long way to go before denuclearization and the complete removal of nuclear weapons capability from the Korean peninsula becomes a reality," she said.

“I’m not entirely convinced Donald Trump and the current U.S. administration have done enough thinking about what this process should look like, and what concessions need to be on the table," Varriale added. "They are not just going to get the North Koreans to give up their nuclear weapons capability without North Koreans thinking they’ll get something in return.”

“It’s really hard to see how this process, at least to the short or medium term, will result in the North Koreans give up their nuclear weapons completely.”

While Varriale said the upcoming Trump summit would be worthwhile, she also fears what might happen should it end without success.

“It does provide the opportunity for the more hawkish elements of the U.S. administration to bolster their argument for the military option, should talks fail,” she said.

One such hawk could be John Bolton, who was named Trump’s new national security adviser last week and has been a vocal proponent of regime change in North Korea. Trump, on the other hand, seems convinced he can bring about denuclearization through striking a deal with Kim.

“Bolton has made it quite clear in the past that he sees the goal of regime change as something to be desired in terms of North Korea,” said Professor Hazel Smith of the School of Oriental and African Studies in London, and author of "North Korea: Markets and Military Rule."

“That’s different from President Trump’s perspective, which is that he thinks he can achieve a nuclear deal on the peninsula with Kim Jong Un. So it’s going to be interesting to see how that plays out,” she said.

Varriale agreed that Bolton's presence in the administration could complicate talks. “I find it incredibly concerning that somebody who has been so vocal on the North Korea nuclear issue ... and is so anti-diplomatic processes and trying to resolve these issues peacefully is in the position he is in in the administration," she said.

“I think that Trump will listen to him," Varriale added, "but I also think Trump wants to solve this problem peacefully, mostly as this will go down on his track record as a major win over the Obama administration. I think that’s probably what’s in the forefront of Trump’s mind right now: how do I make this look like a win for me? And I think to some extent he already thinks he has.”