Earlier this week President Donald Trump responded to the North Korean threat, saying he would unleash “fire and fury” and doubled down on his threat claim during a press conference yesterday.

The Chinese op-ed was published by the Global Times, an English-language newspaper under the auspices of the People’s Daily, itself an official outlet of the Chinese Communist Party. Experts cited by the Washington Post believe the statements reflect the Chinese government’s stance.

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While it suggests that China will not support North Korea if it “launches missiles that threaten US soil and the US retaliates,” the op-ed also says that “if the U.S. and South Korea carry out strikes and try to overthrow the North Korean regime and change the political pattern of the Korean Peninsula, China will prevent them from doing so.”

That relatively fine line reflects the delicacy of China’s relationship with North Korea. China is essentially responsible for North Korea’s existence, having provided substantial military assistance to Northern forces during the Korean War from 1950-1953. For decades, China relied on North Korea as a buffer nation against the U.S. presence in the south and remains North Korea’s largest trading partner and primary source of food and energy. The two countries have a mutual defense treaty dating to 1961.

But North Korean belligerence and changes in China’s place in the world have strained that relationship to new limits, and while the Chinese Communist Party is committed to stability on the Korean peninsula, experts have recently questioned whether China would honor that treaty if war broke out. China has repeatedly called on North Korea halt its nuclear weapons testing program. If it were drawn into a military conflict between North Korea and the U.S., China’s economy could be devastated – the U.S. is its single largest trading partner, making up 18% of overall international trade.