SANTIAGO (Reuters) -Chile's Codelco will partner with global mining giant Rio Tinto for its new Maricunga lithium project, the state miner said on Monday, bringing a major new player into the sector in the world's second-largest producer of the EV battery metal.

The partnership, after a selection process, means Rio Tinto will become just the third private firm in Chile's lithium sector, alongside Chile's SQM and U.S. firm Albemarle that have dominated production there for years.

Global mining firms, car makers and battery companies are racing to secure supply of lithium, an ultra-light metal needed to power the shift toward electric vehicles. South America's "lithium triangle" has the world's largest trove of the metal.

Rio Tinto will contribute up to $900 million to the project, Codelco said in a statement, taking a 49.99% share. Codelco, the world's top copper producer now tasked with spearheading the Chilean state's push into lithium, will control the remainder.

Rio Tinto CEO Jakob Stausholm in a statement said the company aimed to "bring significant investment" to the region.

He noted there could be opportunities to share infrastructure and minimize water use in tandem with a copper exploration project, Nuevo Cobre, that it shares with Codelco in the same region.

The financing is slated to include $350 million when the deal closes, $500 million when a final investment decision is made, and $50 million if commercial production is reached by the end of 2030.

The board for the partnership will consist of three members appointed by Codelco, and two appointed by Rio Tinto, Codelco said. Codelco, while a major player in copper, has little of its own experience mining lithium.

Rio Tinto is meanwhile a major lithium player in neighboring Argentina, the world's fourth-largest producer of the metal, following its acquisition of lithium miner Arcadium.

Rio Tinto is developing the Rincon project in Argentina as well, which will use direct lithium extraction (DLE), an innovative, mostly unproven method that Codelco and Rio Tinto aim to use at Maricunga too.

Codelco Chairman Maximo Pacheco said the deal would be beneficial for its "lithium diversification strategy". The world's biggest copper producer is also teaming up with SQM for a controlling share of its operations in the Atacama salt flat.