A front-end loader is used to reinforce a safety berm inside the open pit at a rare earth facility in California June 29, 2015. (REUTERS/David Becker/File Photo)

Pentagon is seeking proposals to cache a rotating six-month supply of neodymium iron boron (NdFeB) magnets, a type of rare earth magnet essential to weapons manufacturing, according to the document, detailing the latest attempt to weaken China’s control over the rare earths sector.

The request effectively seeks someone to warehouse a six-month supply of the specialized magnets and maintain it for at least 30 months.

China and Japan are the world's largest NdFeB magnet producers. None of the specialized magnets are made in the United States, though a US Naval Research Laboratory scientist invented them here in the early 1980s.