BOAO, China—Chinese President Xi Jinping on Sunday stepped into the growing tensions on the Korean peninsula with a carefully worded warning that no country should be allowed to destabilize the world.

Mr. Xi's language in a speech to the three-day Boao Forum for Asia appeared to be deliberately ambiguous, naming no nation directly. Acknowledging Asian "frictions" and "hot spots," Mr. Xi said, "No one should be allowed to throw a region and even the whole world into chaos for selfish gains."

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