WASHINGTON (AP) — The United States launched a trade complaint yesterday against China at the World Trade Organisation, accusing Beijing of unfairly imposing duties on more than US$3 billion in exports of American-produced automobiles.

The announcement came as President Barack Obama hit the campaign trail in the battleground state of Ohio, where automakers have been affected by the tariffs imposed in December. It underscored how America’s trade relations with rising economic power China could colour the political debate ahead of the November presidential election.

Under WTO rules, countries are allowed to impose punitive tariffs to offset damage from both subsidies and dumping — selling products at below market value — but the US contends that in this and other cases, China has used those remedy measures in an unfair and retaliatory way to hurt American exporters.

Last month, the US successfully challenged Chinese tariffs imposed on American hightechnology steel products and has also disputed tariffs levied on chicken products.

White House spokesman Jay Carney told reporters yesterday that the Chinese duties cover more than 80 per cent of US auto exports to China and fall disproportionately on General Motors and Chrysler because of the actions Obama took to support the auto industry during the financial crisis.

Some critics have contended that the administration’s bailout of the auto sector — which has seen it return to profitability even as the wider economic recovery has stuttered — could leave US products vulnerable to countervailing duties by international competitors claiming it amounted to an unfair subsidy.