The US treasury secretary, Timothy Geithner, is visiting Beijing this week, hoping to gain China's support for US sanctions on Iran's oil industry.
China buys almost one-third of Iran's oil exports and has rejected the US sanctions as a tool to rein in Iran's nuclear programme.
Criticising the new set of sanctions approved by President Barack Obama on New Year's Eve, China has called it improper and ineffective.
Al Jazeera's Melissa Chan reports from Beijing.