The startup known for its Claude chatbot and AI models is valued at a whopping $183 billion. Heavily backed by Amazon, it positions itself as focused on AI safety and responsible development.

Companies based in China, as well as in other countries including Russia, North Korea and Iran, were already unable to access Anthropic's commercial services over legal and security concerns.

Despite the restrictions, some groups "continue accessing our services in various ways, such as through subsidiaries incorporated in other countries", the US firm said in a statement dated Friday.

So "this update prohibits companies or organizations whose ownership structures subject them to control from jurisdictions where our products are not permitted, like China, regardless of where they operate," it said in a statement.

"Companies subject to control from authoritarian regions like China face legal requirements that can compel them to share data, cooperate with intelligence services, or take other actions that create national security risks."

Anthropic said that the update to its terms of service would affect entities more than 50 percent owned, directly or indirectly, by companies based in unsupported regions.

"The safety and security of AI development requires collective commitment to preventing its misuse by authoritarian adversaries," it said.

Anthropic, which is based in San Francisco, was founded in 2021 by former executives from OpenAI, which makes the chatbot ChatGPT.

It said this week it has more than 300,000 business customers, and that the number of accounts on pace to generate more than $100,000 annually is nearly seven times larger than a year ago.