Sen. Bernie Sanders (I-VT) penned a letter to CEOs of artificial intelligence companies and called for a nationwide pause on development, cautioning that Congress will take action tech leaders won’t.

In a letter addressed to OpenAI’s Sam Altman, Anthropic’s Dario Amodei, and Meta’s Mark Zuckerberg, Sanders urged tech giants to “stop building machines that humans cannot control,” according to reporting from Axios.