The Trump administration has launched an investigation into the impact of aluminum dumping by countries like China and Russia citing a threat to US national security.

"Imports have been flooding into the aluminum industry," the US Commerce Secretary Wilbur Ross told reporters at a White House news conference.

Ross said this is in reaction to real world conditions that imports of aluminum have been increasing steadily in recent years, while American producers have experienced cuts in their jobs and plants have been shut down.

The US President Donald Trump will sign an order later on Thursday directing the Commerce Department to complete the investigation as "soon as possible" of dumping. China, the world's top producer and consumer of the metal, is expected to be the worst hit by this executive action.

Since 2015, as many as eight smelters have shut down in the US as a result of influx of foreign aluminum.

The metal is in high demand in the US defence industry, particular for building high-tech planes like F-35, F-16 and C-17.

The investigation will determine if there is sufficient domestic aluminum capacity to meet US defence needs, Ross said.

Although he said China was a major contributor to the global excess capacity in aluminum production, he said imports from other countries, including Russia, were also causing problems.

"The problem we have is there's only one American smelter that produces the high-purity aluminum needed for these uses.

Just one. And that company has been having some problems.

They, in fact, filed a trade case against dumping on their own," Ross said.

"Imports have been flooding into the aluminum industry," Ross said.

The US imported more than 6.5 million metric tonnes of aluminum in 2016 for use in the auto industry, construction and a variety of other sectors. Canada was by far the biggest foreign supplier, with shipments totaling more than 3 million tons, followed by Russia (755,545 tonnes), the United Arab Emirates (557,723 tonnes) and China (518,773 tonnes).

US companies also exported nearly 3 million tonnes of aluminum last year, down slightly from previous years. The biggest destinations were Mexico (764,488 tonnes), China (730,355 tonnes) and Canada (688,427 tonnes), followed by South Korea and Vietnam.

The investigation mirrors a probe the Commerce Department launched last week focusing on the steel industry.