President Barack Obama has reassured China's president Hu Jintao that the United States would remain committed to free trade despite a decision to impose tariffs on Chinese tyres.

"The tyre issue came up. The Chinese remain concerned about it," said a US official told Reuters after the two leaders talked on the sidelines of the United Nations General Assembly in New York city.

"The president noted that we had differences on the issue and said that the US remains firmly committed to free trade and resisting protectionism," the official added.

Reuters noted that Chinese officials called the tyre decision a dangerous act of protectionism and had said they would investigate whether imported US chicken parts and vehicles were being dumped on the Chinese market.

Some US critics of the decision to impose a new 35% duty on Chinese tyres said it sent the wrong message ahead of a meeting of the G20 countries in Pittsburgh tomorrow and Friday.

The White House retorted the decision was merely an enforcement of trade laws.