Microsoft has declared its support for Anthropic and is urging a court to issue a temporary restraining order to prevent the U.S. Department of Defense from designating Anthropic as a supply chain risk for "all existing contracts."

In a legal filing, Microsoft stated that such an order would "facilitate a more orderly transition and prevent disruption to advanced artificial intelligence systems currently in use by the U.S. military."

"Otherwise, Microsoft and other technology companies would be forced to immediately reconfigure existing products and contract arrangements provided to the Department of Defense. This could adversely affect military personnel during a critical period," the company argued.

Last week, the Pentagon formally prohibited the use of Anthropic's technology and classified the company as a supply chain risk—a label historically applied to foreign adversaries.

Under this designation, all defense suppliers and contractors must certify that they do not use Anthropic's models when serving the Department of Defense.

On Monday, Anthropic filed a lawsuit against the Trump administration, describing the government's actions as "unprecedented and unlawful." The company asserted that these measures are "causing irreparable harm to Anthropic," jeopardizing contracts worth hundreds of millions of dollars.