The deal comes days after the Pentagon announces an agreement with seven tech giants to use AI in classified systems.

Tech giants Microsoft, Google and xAI say they will allow the United States federal government access to their new artificial intelligence models for national security testing.

The Center for AI Standards and Innovation (CAISI) at the Department of Commerce announced the agreement on Tuesday amid increasing concerns about the capabilities that Anthropic’s newly unveiled Mythos model could give hackers.

Under the new agreement, the US government will be allowed to evaluate the models before deployment and conduct research to assess their capabilities and security risks.

The agreement fulfils a pledge the administration of US President Donald Trump made in July to partner with technology companies to vet their AI models for “national security risks”.

Microsoft will work with US government scientists to test AI systems “in ways that probe unexpected behaviors”, the company said in a statement. Together they will develop shared data sets and workflows for testing the company’s models, the company said.

Microsoft signed a similar agreement with the United Kingdom’s AI Security Institute, according to the statement.

Concern is growing in Washington over the national security risks posed by powerful AI systems. By securing early access to frontier models, US officials are aiming to identify threats ranging from cyberattacks to military misuse before the tools are widely deployed.

The development of advanced AI systems, including Anthropic’s Mythos, in recent weeks has created a stir globally, including among US officials and corporate America, over their ability to supercharge hackers.

“Independent, rigorous measurement science is essential to understanding frontier AI and its national security implications,” CAISI Director Chris Fall said in a statement.

The move builds on 2024 agreements with OpenAI and Anthropic under President Joe Biden’s administration when CAISI was known as the US Artificial Intelligence Safety Institute. Under Biden, the institute focused on developing AI tests, definitions and voluntary safety standards. It was led by Biden tech adviser Elizabeth Kelly, who has since joined Anthropic, according to her LinkedIn profile.

CAISI, which serves as the government’s main hub for AI model testing, said it had already completed more than 40 evaluations, including on cutting-edge models not yet available to the public.

Developers frequently hand over versions of their models with safety guardrails stripped back so the centre can probe for national security risks, the agency said.

xAI did not immediately respond to a request for comment. Google declined to comment.

On Wall Street, Microsoft’s stock was down by 0.6 percent in midday trading on the heels of the announcement. Alphabet, Google’s parent company, on the other hand was trending in the opposite direction. The stock was up 1.3 percent. xAI is not publicly traded.

The announcements followed an agreement between the Pentagon and seven major tech companies – Google, Microsoft, Amazon Web Services, Nvidia, OpenAI, Reflection and SpaceX – to use their AI systems across classified computer networks.

The Department of Defense said the agreement will provide their resources to help “augment warfighter decision-making in complex operational environments”.

Notably absent from the list is AI company Anthropic after its public dispute and legal fight with the Trump administration over the ethics and safety of AI usage in war.