Friendship or leverage: Why is Xi Jinping in North Korea?

Beijing has "mixed feelings" about the growing partnership between Pyongyang and Moscow, says Lee Seong-hyon, a visiting scholar at the Harvard University Asia Center.

On one hand, the partnership "distracts Washington and complicates US strategy in multiple theaters, which indirectly benefits China", Lee says.

But, he adds, expanding military cooperation between Russia and North Korea could spark a stronger trilateral military response from the US, Japan and South Korea, which would worry Beijing.

That is also why China is not endorsing Pyongyang's nuclear programme - because that would increase US involvement in the region and its alliances here.

But neither is China confronting the issue head on. In 2022, China and Russia vetoed a US-led United Nations resolution to impose new sanctions over North Korea's missile tests.

If China takes a strong stance against Pyongyang's nuclear programme, "this would only push North Korea more into the arms of Putin", says Victor Cha, president of the foreign policy department at the Center for Strategic and International Studies.

But Kim cannot afford to alienate his biggest source of aid either.

China's exports to North Korea surged to around $2.3bn (£1.7bn) last year, the highest level in six years. Passenger train services between Beijing and Pyongyang restarted earlier this year after a six-year hiatus.

Analysts say this too is a calculated effort by Beijing to pull Pyongyang back into its orbit.

For Kim, it is the pragmatic choice. If the war in Ukraine ends, Russia's need for North Korean support could diminish. And unlike an isolated Putin, Xi has been welcoming world leaders to Beijing.

So Kim needs to ensure he is not left relying on a weakening partner.

But this relationship was troubled from the start.

Kim inherited power with priorities that differed from his father's. While Kim Jong Il visited China repeatedly and relied on Beijing's backing, his son moved quickly to accelerate North Korea's nuclear programme. In his first six years in power, Kim oversaw around 90 ballistic missile tests and four nuclear detonations - more than his father and grandfather combined.

This alarmed Beijing. And then the execution of Kim's uncle, Jang Song Thaek, seen by China as a stabilising figure, deepened the rift.

Xi responded with rare diplomatic signals of displeasure, visiting South Korea in 2014 before ever meeting Kim: a move that was widely viewed as a snub.

North Korea responded by calling China a "turncoat and our enemy."

It was only in 2018, as sanctions over his nuclear programme began to bite, that Kim made his first known foreign trip.

He got on his armoured train and headed to Beijing. That meeting marked the start of a cautious recalibration.

Kim would go on to meet US and South Korean leaders, but it was always after consulting China. The message was clear: Pyongyang would not negotiate without Beijing's backing.

Today, North Korea serves as both buffer and burden for China. It keeps US forces at arm's length, but its weapons tests destabilise the region.

Kim, meanwhile, wants Chinese protection - without Chinese control.

Neither side fully trusts the other. But for now, they both believe they need the other and that is enough to keep them talking.

Additional reporting by Kelly Ng