Chinese President Xi Jinping has doubled down on his country's alliance with North Korea, telling Kim Jong Un that Beijing's support is "unshakable" no matter how the world changes. The message came in letters exchanged between the two leaders, published Friday by North Korea's state-run Korean Central News Agency.

Xi said the Chinese Communist Party and government would continue to attach great importance to the traditional friendship between the two countries and would firmly support North Korea's socialist cause under Kim. It's a clear signal that, despite international pressure, China isn't backing away from its neighbor.

Kim, in his letter, said cooperation and friendship between the two countries had reached a "new strategic level." That's diplomatic language for: we're getting even closer. The exchange coincided with the 65th anniversary of the Treaty of Friendship, Cooperation and Mutual Assistance, signed on July 11, 1961. That treaty is China's only active mutual defense pact—meaning if North Korea is attacked, China is obligated to help.

The letters weren't the only sign of tightening ties. North Korean Premier Pak Thae Song arrived in Beijing on Friday for a three-day visit to commemorate the anniversary. And last month, Xi made his first trip to Pyongyang in seven years, where he and Kim agreed to deepen cooperation across political, economic and cultural sectors.

For investors, the message is clear: China isn't distancing itself from North Korea anytime soon. That could have implications for geopolitics, sanctions enforcement, and regional stability—all factors that move markets.