At stake are contracts to explore and produce some 400,000 tonnes of lithium.

"The business of lithium is sure to be one of the priorities on the shared agenda between Chile and Mexico," says Mexican Foreign Minister.

President-elect Gabriel Boric has said Chile should not repeat its "historic mistake" of privatizing resources such as lithium, a vital ingredient of electric car batteries.

Mounting opposition to new lithium contracts in Chile is the latest indication of just how difficult it will be for the world to churn out the building blocks of the clean energy transition.

UN experts and rights groups estimate more than a million people have been detained in camps in the far-western Chinese region.

The licences in the Upper Rhine Valley cover 325 sqkm and increase Vulcan's granted licence area to more than 1,000 sqkm.