NEW YORK (BLOOMBERG) - The world's largest rare-earth producer outside of China will prioritise the United States military's needs when it starts production at a plant it is building in Texas, the company's chief executive officer said.

While defence applications are small compared to commercial uses, the military has been successful in creating "viable supply chains" across the industry, and that makes it a high priority, Lynas Corp's Amanda Lacaze said in an interview in Chicago on Thursday (June 6).

Rare earths - a group of 17 vital elements used in missile systems, electric vehicles, computer screens and other tech devices - have been thrown into the limelight after China signalled it may restrict shipments to the US.

Lynas has been in talks with the US Department of Defence and the Defence Logistics Agency "pretty much for as long as I've been in the job and I'm thinking before that as well", she said.

Negotiations for supply to the DoD and the DLA gave Lynas the confidence to enter into a joint venture with Blue Line Corp to build, in Texas, the only separation plant for heavy rare earths outside of China, she said.

The US stressed the urgency to ensure it doesn't get cut off from supply, with Commerce Secretary Wilbur Ross promising "unprecedented action" on Tuesday to secure the nation's access to the raw material.

The country relies on China for 80 per cent of its imports, according to the US Geological Survey.

Defence contractors account for just 1 per cent of the US rare-earth demand, or about 0.09 per cent of global consumption, Raymond James analysts including Mr Pavel Molchanov, said in a note on Monday.

China produced about 71 per cent of the world's output last year, according to the US Geological Survey.

Lynas' plant in Texas will have the capacity to produce at least 1,200 tonnes of so-called SEG oxide, a group of heavy rare-earth elements, Ms Lacaze said.