They do. DoD made a deal with MP Minerals (Mountain Pass, CA) in 2024. DoD will buy rare earths at a guaranteed price which is well above the world price.[1]

This followed a 2021 deal with General Motors to insure GM's magnet supply.[2] That resulted in building a modest magnet plant in an industrial park in Texas, using MP Minerals ore.

This deal expanded in 2025, with DoD taking a majority stake in MP Minerals.[3]

The history here is that the price goes up and down so much that the Mountain Pass mine has been shut down twice since the 1990s. There were two bankruptcies. The most recent glut and price crash was in 2015.[4]

The process has four steps: 1) mining, 2) beneficiation, where mixed rare earth ores are separated out, 3) chemical separation, where the individual rare earths are separated, and 4) magnet metal making. For years, 3) wasn't done in the US, and MP Minerals was shipping ore to China for processing.

[1] https://bidenwhitehouse.archives.gov/briefing-room/statement...

[2] https://investor.gm.com/news-releases/news-release-details/g...

[3] https://mpmaterials.com/news/mp-materials-announces-transfor...

[4] https://en.wikipedia.org/wiki/MP_Materials

Commenter meant straw buyers as in buyers of Chinese rare earths that do so at the behest of the US DoD while under the guise of buying the metals for their own use internal to whatever country they are based in.