WASHINGTON - A US trade panel has approved a Commerce Department investigation that could lead to duties on hundreds of millions of dollars of aluminium goods from China.

The US International Trade Commission (ITC) voted 6-0 that there was enough evidence that US producers of aluminum "extrusions", used in the auto industry and other sectors, have been harmed by the imports to proceed with the probe.

The United States imported more than $US500 million ($A559.16 million) of the goods from China in 2009. The Commerce Department launched its investigation last month after receiving a petition from US producers complaining of unfair Chinese practices.

The manufacturers have asked for anti-dumping duties of roughly 33 per cent to offset what they says are below-market prices on the Chinese-made product. They also want additional duties to offset Chinese government subsidies.

The Commerce Department will set preliminary duties in coming months and final duties within a year or so. The ITC will vote a second time and could strike down any duties.

US construction and automobile industries are two of the biggest consumers of aluminum extrusions, which are made by squeezing heated aluminum into a mold. Uses include doors and window frames, structural framing systems, roofing and exterior cladding.

The case follows a number of other US industry complaints against their Chinese competitors, and comes just before US Commerce Secretary Gary Locke is headed to China on a trade mission to promote US clean energy exports.

At a briefing ahead of that trip, Locke defended US anti-dumping and countervailing duty actions against Chinese charges that they were protectionist.

The United States only takes action when an industry files a petition and wins a decision in its favour, he said.

Also, less than three per cent of US imports from China have been hit by anti-dumping or countervailing duties, he said.

The United States imported $US296.4 billion worth of goods from China in 2009 and had a $US226.8 billion bilateral deficit.

Both Canada and Australia have already moved to curb imports of aluminum extrusions from China.

China's own aluminum extrusion industry suffers from severe overcapacity because of massive expansions by both state and private producers, in part to get around Chinese restrictions on aluminum ingot exports.