In a statement earlier on Thursday, a senior Pentagon official said the supply chain risk designation was “effective immediately.”
Amodei wrote that Anthropic had received a letter from the defence department the previous day designating it a risk, noting that the designation “has a narrow scope.”
“The law requires the Secretary of War to use the least restrictive means necessary to accomplish the goal of protecting the supply chain”, he wrote.
“Even for Department of War contractors, the supply chain risk designation doesn’t (and can’t) limit uses of Claude or business relationships with Anthropic if those are unrelated to their specific Department of War contracts.
The AI developer had been in talks with the Department of Defense in recent days.
Those talks did not prove fruitful, according to a person familiar with Anthropic who asked not to be identified, in part because of how President Donald Trump and other members of his administration had publicly berated the company.
Leadership at Anthropic had thought last week the two sides were near a resolution, after weeks of back and forth. Then Trump posted on his Truth Social platform that he was directing all federal agencies to stop using Anthropic, the person familiar added.
“We don’t need it, we don’t want it, and will not do business with them again!” Trump wrote in the Friday post.
Hegseth followed up with a post on X, writing that Anthropic would be “immediately” designated a supply chain risk, prohibiting any business working with the military from “any commercial activity with Anthropic”.
Anthropic said it had received no communication from the White House or the Pentagon that these statements were coming.
According to a person familiar with discussions, the feeling inside Anthropic is that it is disliked by some in the Trump administration as its chief executive has not been among the tech leaders to donate large sums to Trump or publicly praise him.
On Thursday, tech giant Microsoft said that it would continue to embed Anthropic technology in products for its clients with the exception of the US Department of Defense.
“Our lawyers have studied the designation and have concluded that Anthropic products, including Claude, can remain available to our customer, it told the BBC in a statement.
“We can continue to work with Anthropic on non-defense related projects,“ it continued.
The Department of War is a secondary name given by Trump to the Department of Defense.
A Pentagon official said Thursday: “From the very beginning, this has been about one fundamental principle: the military being able to use technology for all lawful purposes.”
“The military will not allow a vendor to insert itself into the chain of command by restricting the lawful use of a critical capability and put our warfighters at risk.”