China is warning the United States not to escalate its attacks on Yemen’s Houthi rebels, as the conflict in the Red Sea threatens Beijing’s economic and diplomatic interests.

The Houthis’ months-long campaign to restrict maritime traffic through key Middle Eastern waterways poses a unique threat to China, which relies heavily on the Suez Canal and the Bab-el-Mandeb Strait to transport Chinese goods to European markets. China is also more reliant than the US on oil and gas imports from Saudi Arabia, the United Arab Emirates, Iran, and Qatar.

“China is concerned about the escalating tensions in the Red Sea and calls on relevant parties to exercise calm and restraint to prevent the conflict from escalating,” Beijing’s Foreign Ministry spokesman Mao Ning told reporters Friday. “China calls on relevant parties to play a constructive and responsible role in keeping the Red Sea safe and stable, which serves the common interests of the international community.”

China declined to join a US-led coalition of forces known as Operation Prosperity Guardian, which began policing the Red Sea last month.

On a broader level, the growing military exchanges between the United States and the Houthis endangers China’s Mideast diplomatic interests. Last spring, Beijing surprised Washington by mediating a normalisation of relations between Saudi Arabia and Iran, the Houthis’ main military ally. The agreement was based, in part, on Iran’s promise to China to cut off military supplies to the Yemeni militia and limit Houthi attacks on Saudi and international targets.

However, Tehran has recently praised the Houthis’ Red Sea operation, and Iran’s elite military unit, the Islamic Revolutionary Guard Corps, has embedded personnel with Yemeni militia forces, according to US and Arab officials.