North Korean leader Kim Jong Un met with China’s president in a secret trip to Beijing

North Korea’s leader, Kim Jong Un, secretly traveled to Beijing to meet with Chinese President Xi Jinping, Chinese state television reported after intense speculation about the North Korean leader’s whereabouts.

The trip was Kim’s first outside North Korea since taking power in 2011, and included his first sit-down with another head of state. The timing of the meeting is also notable, ahead of Kim’s potential face-to-face with President Donald Trump.

According to a report in China’s state-run Xinhua news agency, Kim and President Xi reaffirmed the friendship between the two countries and discussed potential talks with the United States. The North Korean leader also suggested he was open to denuclearization.

This is similar to what Kim relayed to the South Koreans last month — before Trump accepted the unprecedented face-to-face meeting with Kim — though some experts are skeptical of North Korea’s motivations. The United States has said it will not accept anything less than the denuclearization of North Korea.

Kim’s visit also clears up the mystery of a heavily secured and slow-moving train spotted crawling into Beijing on Monday night. According to the New York Times, previous North Korean leaders had relied on this bulletproof transport for their rare foreign trips, and so it made sense that Kim would follow the tradition. But no one would confirm the leader of the isolated country had crossed over the North Korean border, and China had remained mum until now.

Kim reportedly came to China on Xi’s invitation. It makes sense that China, as North Korea’s ally, might want to check in with Kim before his potentially historic meetings with the United States and South Korea. Kim is expected to attend a summit with South Korean President Moon Jae-in on the Korean border in April. The meeting with Trump is tentatively scheduled for May.

As the Times pointed out, relations between North Korea and China have been a bit strained in recent months. Beijing has joined the United States and the rest of the world in supporting harsh UN sanctions against North Korea, and it was also wary of North Korea’s ramped up nuclear testing.

China, however, is unlikely to stay on the sidelines as Kim attempts negotiations the US and South Korea with its regional interests at stake. And it’s probably equally unlikely Kim would make diplomatic overtures to his adversaries without some help, or muscle, from the Chinese.

“Kim Jong Un wants to allay fears of China’s leaders that North Korea could grow closer to the US,” Kim Jae-chun, a professor at South Korea’s Sogang University told the Financial Times. “North Korea will need to mend fences with China one way or another. It is necessary, and it is better to do it sooner rather than later.”

Soon after China confirmed Kim’s visit to Beijing, the New York Times reported that the US and South Korea have reached a bilateral trade agreement. Trump has advocated one-on-one agreements over multilateral pacts in an effort to make deals that are more “fair” to the US. This is the first major one-on-one agreement the Trump administration has made so far, and it’s likely as much of an attempt to bolster relations between the two allies ahead of North Korea talks, as it is to win America the best deals.

In addition to the new trade agreement, Kim’s visit to China comes amid other shifts in the diplomatic landscape. Tensions between the United States and China have escalated after Trump said he plans to hit China with $60 billion in tariffs, and Beijing plans to retaliate. Trump also just announced he is replacing National Security Adviser H.R. McMaster with the extremely hawkish John Bolton, who has said in the past that the US should declare war on North Korea.