A Chinese-backed militia is protecting new rare earth mines in eastern Myanmar, according to four people familiar with the matter, as Beijing moves to secure control of the minerals it is wielding as a bargaining chip in its trade war with Washington.

China has a near-monopoly over the processing of heavy rare earths into magnets that power critical goods like wind turbines, medical devices and electric vehicles.

But Beijing is heavily reliant on Myanmar for the rare earth metals and oxides needed to produce them: the war-torn country was the source of nearly half those imports in the first four months of this year, Chinese customs data show.