The United States and China have announced new anti-dumping steps against each other over aluminum and nylon, raising the threat of new tensions over trade and currency that had eased in recent weeks.
The US Commerce Department said Wednesday it was launching an investigation into whether Chinese extruded aluminum products were being dumped, or sold at improperly low prices, due to government subsidies or other aid.
On Thursday, China's Commerce Ministry said it was imposing anti-dumping duties of up to 96.5 percent on imports of polycaprolactam, or nylon 6, from the United States, Europe, Russia and Taiwan.
The latest moves could reignite strains over US complaints about China's currency controls, which critics say keep the Chinese currency undervalued and give its exporters an unfair price advantage.
The two sides have made a series of conciliatory gestures in recent weeks - including a visit by Chinese President Hu Jintao to Washington.
The two governments have launched a series of trade cases over access to each other's markets for tires, steel, movies, music and other goods.
Products cited in the latest US complaint are used in making window and door frames and sills, gutters, and solar power frames.
The Commerce Department said their prices were alleged to be 32.5 to 33.3 per cent too low. The department said it would issue a preliminary report May 17 and a final determination in May.