Here's my understanding of the situation:

Anthropic signed a contract with the Pentagon last summer. It originally said the Pentagon had to follow Anthropic's Usage Policy like everyone else. In January, the Pentagon attempted to renegotiate, asking to ditch the Usage Policy and instead have Anthropic's AIs available for "all lawful purposes"1. Anthropic demurred, asking for a guarantee that their AIs would not be used for mass surveillance of American citizens or no-human-in-the-loop killbots. The Pentagon refused the guarantees, demanding that Anthropic accept the renegotiation unconditionally and threatening "consequences" if they refused. These consequences are generally understood to be some mix of :

canceling the contract
using the Defense Production Act, a law which lets the Pentagon force companies to do things, to force Anthropic to agree.
the nuclear option, designating Anthropic a "supply chain risk". This would ban US companies that use Anthropic products from doing business with the military2. Since many companies do some business with the government, this would lock them out of large parts of the corporate world and be potentially fatal to their business3. The "supply chain risk" designation has previously only been used for foreign companies like Huawei that we think are using their connections to spy on or implant malware in American infrastructure. Using it as a bargaining chip to threaten a domestic company in contract negotiations is unprecedented.

https://www.astralcodexten.com/p/the-pentagon-threatens-anthropic