Hong Kong (CNN) A surprise visit by North Korean leader Kim Jong Un to China may indicate Pyongyang's need for support from its closest ally ahead of upcoming summits with South Korea and the US.

Kim met with Chinese President Xi Jinping and other high ranking officials in Beijing this week. Observers had said it would have been highly unusual for him to meet US President Donald Trump without seeing Xi first.

Prior to the Beijing trip, Kim had never met a foreign leader since he took power in 2011. China is North Korea's number one trading and economic partner, and is Pyongyang's only major military ally.

Kim and South Korean President Moon Jae-in are due to meet next month, and a proposed meeting with Trump is due to take place by May. Aidan Foster-Carter, an honorary senior research fellow at Leeds University, said it would have been almost unthinkable for Kim to meet with Moon and Trump having never met Xi, given the importance of the Sino-Korean alliance.

Key alliance

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