Rio Tinto, Eramet and LG Energy are among 30 companies that have submitted proposals to develop lithium extraction technology for a Chilean salt flat in the early stages of exploration, state-run mining body ENAMI said.

Chile is seeking to develop the salt flat known as Salares Altoandinos for lithium mining.

ENAMI has asked bidding companies to detail step-by-step plans to test the brine deposits of the salt flats, outline potential processes to reach battery grade lithium, and to state whether they had a plan to assess the environmental impact of brine reinjection.

"The objective ... is to become acquainted with state of art development of technological processes for lithium extraction that are being developed worldwide," ENAMI said in a statement on Monday.

Rio Tinto, the world's biggest iron ore producer, is one of the few large mining companies betting on lithium, with a project in Argentina where it expects to start production by year's-end.

France's Eramet is also developing a lithium project in Argentina, with production expected to start this year, and last year acquired salt flats in Chile for which it is now pursuing exploration and mining rights.

President Gabriel Boric last year launched a policy aimed at boosting the state's role in the lithium industry in Chile, which has the world's largest reserves of the metal.

Boric also announced an ambitious plan to phase out traditionally used evaporation ponds and require the use of direct lithium extraction (DLE) technology, which is still unproven.