OpenAI on Monday said it raised US$40 billion in a new funding round that valued the ChatGPT maker at US$300 billion, the biggest capital-raising session ever for a startup.

The infusion of cash comes in a partnership with Japanese investment giant SoftBank Group and "enables us to push the frontiers of AI research even further," the San Francisco-based company said in a post on its website.

"Their support will help us continue building AI systems that drive scientific discovery, enable personalised education, enhance human creativity, and pave the way toward AGI (artificial general intelligence) that benefits all of humanity," the company said.

AGI refers to a computing platform with human-level intelligence.

SoftBank said in a release that it is on a mission to realise Artificial Super Intelligence (ASI) that surpasses human intelligence, and that OpenAI is the partner closest to achieving that goal.

"The advancement of OpenAI's AI models is key to achieving AGI and ASI, and massive computing power is essential," SoftBank stated in its rationale for the latest investment in the company.

SoftBank is to pump US$10 billion into OpenAI to start, and US$30 billion more by the end of this year pending certain conditions.

OpenAI plans to scale its infrastructure and "deliver increasingly powerful tools for the 500 million people who use ChatGPT every week." (AFP)