US Government Intervenes to Limit UK Access to Latest OpenAI and Anthropic Models

The United Kingdom’s ambitions to remain at the vanguard of global artificial intelligence safety have faced a significant setback following reports that the US government has moved to restrict the UK’s AI Security Institute (AISI) from accessing the latest models from industry leaders OpenAI and Anthropic. The decision, which marks the second time in a single month that the UK testing body has been sidelined, highlights growing tensions between international cooperation on AI safety and the national interests of the United States.

According to reports, the AISI will not be granted the pre-release access it typically requires to evaluate the safety and security profiles of several high-profile models launched on September 22. These include Anthropic’s Claude Opus 5.5 and a new suite of models from OpenAI, designated as GPT-6 Sol and GPT-6 Luna. While the AISI has historically functioned as a primary auditor for frontier AI systems before they reach the general public, this latest development suggests a shift in how the most powerful AI technologies are being shared with international partners.

The intervention reportedly originated from the highest levels of the US executive branch. Sources familiar with the matter indicated that the White House, specifically through the Office of the National Cyber Director, requested that both OpenAI and Anthropic withhold these specific models from the UK testing agency until they had undergone a thorough review by American authorities. This move effectively places the US government as the primary gatekeeper for frontier AI models developed within its borders, prioritizing domestic oversight over the collaborative, international framework the UK has sought to establish.

A senior US official defended the move as a matter of standard procedure and national policy. The justification provided was straightforward: because these are American companies developing what are considered "frontier" models—systems that represent the absolute edge of current technological capability—the US government maintains that its own agencies must have the first opportunity to assess potential risks. This policy, the official noted, is being applied consistently to every new major iteration of AI technology that emerges from the US tech sector.

The UK’s AI Security Institute, which is backed by the British government, was established with the specific mandate of conducting rigorous research into the safety of AI models. Its work involves a delicate balance of technical red-teaming, safety benchmarking, and close collaboration with both academic researchers and industry stakeholders. For the AISI, pre-release access is not merely a courtesy; it is the cornerstone of its operational model, allowing the institute to identify vulnerabilities, biases, or dangerous capabilities before a model is integrated into the global digital infrastructure.

Another blow for the AISI

The denial of access to GPT-6 Sol, GPT-6 Luna, and Claude Opus 5.5 represents a deepening trend of exclusion for the UK body. If the reports are confirmed, it would be the second time in September that the AISI has been prevented from performing its core function on a major release. Earlier this month, the institute was notably left out of the evaluation process for Anthropic’s Mythos 5.1 model.