SoftBank Group is in discussions to invest as much as $25 billion in OpenAI, in a move that would potentially make it the AI startup's biggest backer.

The Japanese investment company is in talks to put in between $15 billion and $25 billion, according to a person familiar with the matter. That would be in addition to the $15 billion that Masayoshi Son’s SoftBank has committed to Project Stargate, the Texas-based joint venture with OpenAI to build data centers and other AI infrastructure to support the company behind ChatGPT, the person said, asking not to be named discussing private talks.

The plans are at an early stage and may not result in an investment, the person said. Representatives of SoftBank and OpenAI declined to comment.

Son stood alongside OpenAI CEO Sam Altman when U.S. President Donald Trump announced the Stargate venture this month, and the two CEOs have been in contact for many years over their shared interest in advancing artificial intelligence development. Along with joint venture partners Oracle and Abu Dhabi-backed MGX, Stargate plans to deploy $100 billion initially and invest as much as $500 billion over four years.

OpenAI’s biggest investor Microsoft declined to comment. The Financial Times first reported the talks were in progress.

OpenAI hungers for more data center capacity to make its AI more powerful. It’s now facing a market crowded with rivals, emboldened by Chinese startup DeepSeek’s apparent success at matching OpenAI’s capabilities at a fraction of the cost. The U.S. firm has so far relied on Microsoft for much of its cloud and computing needs.

SoftBank has been in search of an opportune moment to enter the lucrative AI hardware market after years of uneven bets on AI startups via the Vision Fund.

Son and OpenAI’s Altman first met in 2019, when Son offered OpenAI $1 billion in investment, which never materialized. The two have since bonded over their shared concerns around the shortage of semiconductors needed to power AI applications, and the Vision Fund invested $500 million in the startup and launched a $1.5 billion tender to buy more stock from OpenAI employees last month.

News of SoftBank’s possible investment helped bolster a rise in Asian chip-related stocks including Advantest. SoftBank’s shares were down 1% Thursday morning in Tokyo.

"It makes sense that Nasdaq and semiconductor-related stocks are being bought, but SoftBank, which is putting up the money, isn’t going to see the same buying momentum,” said Takehiko Masuzawa, head of equity trading at Phillip Securities Japan.

Tech industry players including Elon Musk have questioned the lack of details around Stargate and its financing. The xAI founder expressed doubt about whether companies that joined Trump’s announcement could follow through on their financial commitments.

SoftBank had roughly $25 billion in cash and cash equivalents at the end of September as well as holdings in hundreds of startups and a 90% stake in chip designer Arm Holdings that it could tap to finance the bet.

But skepticism persists about whether Stargate actually amounts to a dramatic increase from previously announced data center build-out plans. Son visited Mar-a-Lago just last month to announce that SoftBank would spend $100 billion in the U.S. over the coming presidential term, and Project Stargate draws from that effort, according to a person familiar with the matter.