China Zhongwang Holdings Ltd, the country's largest aluminum extrusions maker, is seeking official backing to help it fight a US anti-dumping and countervailing duty charges.

"We are closely cooperating with departments, including the Ministry of Commerce and the China Nonferrous Metals Industry Association, to defend our interests," said an official from Zhongwang, who asked not to be named.

Zhongwang is China's largest exporter to the United States of aluminum extrusions, which are widely used in window frames and automotive parts. Its sales to the US reached 5 billion yuan last year.

"Our competitive edges are obvious when compared with counterparts in the US. We have lower labor and management costs," said the official, who added the company didn't violate any World Trade Organization rules in its operations.

The US International Trade Commission in May approved a US Commerce Department investigation that there was enough evidence to show aluminum extrusions imported from China had harmed the domestic industry, leading to a further probe into aluminum goods made in China.

The Commerce Department started its investigation in April after receiving a petition from the United Steel Union and the Aluminum Extrusion Fair Trade Committee complaining of unfair Chinese practices in the form of Chinese government subsidies to its exporters.

The department is scheduled to make a preliminary countervailing determination in June and an anti-dumping determination in September.

The US investigation follows a similar move by the European Union and Australia, which imposed an anti-dumping duty of as high as 30 percent on aluminum foil and 16 percent on aluminum extrusions from China last July and November.

Chinese manufacturers emerged in the global market only 10 years ago. They have much more sophisticated equipment and a higher industry concentration than overseas rivals that help them reduce costs, said Alex Aw, general manager of the export department of China's Asia Aluminum Group.

"It's totally a mistake to say that our advantages are from government's subsidies," Aw said, adding that he anticipated action by the Chinese government to defend its interests.

According to the US government, imports of aluminum extrusion from China rose 90 percent from 2007 to 2009 and were valued at $514 million.

"We have been aware of the investigation. We will sell our products in China from the US if the case is approved, otherwise we will make losses," said Irene Liu, a senior manager at Yuan Sheng Aluminum MFG Corp, which operates factories in Suzhou and Dongguan.

Many domestic aluminum firms said the anti-dumping duties imposed on them would be more than 10 percent if the US finally approves the case.