China's Foreign Ministry said on Monday it was irresponsible to blame anyone for an attack on Saudi Arabia's oil facilities without conclusive facts, striking a cautious note after the United States blamed Iran.
Yemen's Iran-aligned Houthi group has claimed responsibility for the attack, but U.S. Secretary of State Mike Pompeo said there was no evidence the attack came from Yemen.
U.S. President Donald Trump said on Sunday the United States was "locked and loaded" for a potential response to the attack.
A senior U.S. official told reporters that evidence from the attack, which hit the world's biggest oil-processing facility, indicated Iran was behind it. Iran has denied this.
Speaking in Beijing, Chinese Foreign Ministry spokeswoman Hua Chunying appealed for calm and restrain.
"Pondering who is to blame in the absence of a conclusive investigation I think is in itself not very responsible. China's position is that we oppose any moves that expand or intensify conflict," Hua told a daily news briefing.
"We call on relevant parties avoid taking actions that bring about an escalation in regional tensions. We hope all sides can restrain themselves and can jointly safeguard the peace and stability of the Middle East."
China has close economic, diplomatic and energy relations with both Riyadh and Tehran and has long had to tread carefully in its ties with both.
Saudi Arabia is China's top oil supplier year to date.
Saudi Arabia's King Salman visited Beijing in 2017, and Saudi Crown Prince Mohammed bin Salman came to China earlier this year.
Iranian Foreign Minister Mohammad Javad Zarif met the Chinese government's top diplomat, State Councillor Wang Yi, in Beijing late last month.