Prior to Trump’s decision on Friday, Anthropic received support in its stance against the government.

OpenAI boss Sam Altman offered support to rival AI executive Amodei. He sent a note to staff stating that he had the same “red lines” when it came to the application of the firms’ products.

In the note seen by the BBC, Altman said any OpenAI contracts for the military would also reject uses that were “unlawful or unsuited to cloud deployments, such as domestic surveillance and autonomous offensive weapons”.

He later confirmed on X that OpenAI had reached a deal with the Department of War to use its AI models on classified cloud networks.

Amodei is a long-time figure in tech, rising to prominence as an early employee of OpenAI. He and a handful of other OpenAI employees left the company to found Anthropic after disagreements with Altman.

The two startups now compete directly for users and corporate customers with an evolving offer of AI chatbots, agents and other tools.

“I do not fully understand how things got here; I do not know why Anthropic did their deal with the Pentagon and Palantir in the way they originally did it,” Altman wrote in his company memo.

“But regardless of how we got here, this is no longer just an issue between Anthropic and the [Department of War] DoW; this is an issue for the whole industry and it is important to clarify our stance.”

Hegseth on Tuesday called Amodei to Washington DC for a meeting amid growing tensions. It culminated in two contradictory ultimatums if Anthropic refused to grant the department free rein of its tools.

Hegseth said he would invoke the Defense Production Act, allowing the government to use Anthropic’s products as it saw fit, and deem it a “supply chain risk”.

By Thursday, Amodei said he would rather stop working with the Pentagon than acquiesce to such threats.

A former official with the DoD, who asked not to be named, told the BBC that Anthropic appeared to have the upper hand in the fight.

“This is great PR for them and they simply do not need the money,” the former official said.

Anthropic’s work with the Pentagon is part of a contract worth $200m (£149m). The company’s most recent valuation came earlier this month and put the company’s worth at $380 billion, based on its current revenue and future expected earnings.

The former official added that the defence department’s basis for threatening Anthropic with invoking either the Defense Production Act and being labelled a supply chain risk was “extremely flimsy”.