China’s foreign ministry said imposing unilateral sanctions on Zhuhai Zhenrong based on US law was “unreasonable”.
The US said on Thursday Zhuhai Zhenrong was one of three international firms to be punished for dealing with Iran.
It comes as Chinese Premier Wen Jiabao visits Arab oil-producing nations amid fears of major sanctions-related disruption to Iranian oil exports.
Mr Wen visited Saudi Arabia – China’s biggest source of imported oil – on Saturday.
He told Saudi Prince Nayef both countries are “in important stages of development and there are broad prospects for enhancing cooperation,” China’s state-run news agency Xinhua reports.
During his visit, state-run Saudi oil giant Aramco and China’s Sinopec finalised an initial agreement to build an oil refinery in the Red Sea city of Yanbu to deal with 400,000 barrels per day.
Later on Saturday, Beijing denounced Washington’s decision to punish Zhuhai Zhenrong.
“Imposing sanctions on a Chinese company based on a domestic (US) law is totally unreasonable and does not conform to the spirit or content of the UN Security Council resolutions about the Iran nuclear issue,” Foreign Ministry spokesman Liu Weimin said.