SoftBank could invest $15 billion to $25 billion directly into Microsoft-backed OpenAI, some of which may be used to pay for OpenAI's commitment to Stargate, the person said.
Stargate is a joint venture by Oracle (ORCL.N), OpenAI and SoftBank, that plans to invest up to $500 billion to help the United States stay ahead of China and other rivals in the global AI race.
SoftBank's investment would be on top of the $15 billion it has already committed to Stargate, the person said, adding the talks are at an early stage.
The latest OpenAI investment talks were reported by the Financial Times earlier on Thursday.
Tech news website The Information reported previously that SoftBank was planning to invest a total $40 billion into Stargate and OpenAI and had begun talks to borrow up to $18.5 billion in financing, backed by its publicly-listed assets.
The Stargate venture was announced by U.S. President Donald Trump, SoftBank CEO Masayoshi Son, OpenAI CEO Sam Altman and Oracle Chairman Larry Ellison at the White House last week.
However, since then, a little-known startup from China, DeepSeek, has upended markets with a free artificial intelligence assistant it said was developed cheaply using lower-cost chips and less data than U.S. rivals.
SoftBank's share price surged on news of the Stargate project but has fallen more than 12% since the Deepseek-induced selloff began.
Its shares were down around 1% in morning trading on Thursday.
SoftBank CEO Son's plan to take a large stake in OpenAI and meet its Stargate commitments has been vetted by senior executives and the board at OpenAI, the Financial Times reported. Last year, SoftBank took a $1.5 billion stake in OpenAI.
OpenAI and SoftBank did not respond to Reuters' requests for comment.
