OpenAI is looking to close a $40 billion fundraising round that would value the company at $340bn - more than doubling its value since October, despite DeepSeek concerns.

The deal would be led by SoftBank, with Masayoshi Son's company looking to invest between $15bn and $25bn, which would make it the largest investor in the company by dollar amount. With Microsoft having invested less, but earlier, it may still have a bigger equity stake.

SoftBank is also the joint largest backer of OpenAI's $500bn Stargate AI data center effort, with $19bn expected to be invested. OpenAI's $19bn Stargate investment, meanwhile, could likely come from this funding round, considering the loss-making company has only raised $20bn to date.

The generative AI business still plans to expand its use of Microsoft Azure data centers along Stargate, particularly for inference workloads, which will also continue to drain its resources.

Should OpenAI raise the $40bn, it would be a record single funding round for a private company, vaulting its valuation beyond that of TikTok owner ByteDance, and only $10bn behind SpaceX. This is even though the release of a cheaper Chinese model from DeepSeek caused tech stocks to stumble on fears that high AI investments would be undercut.

However, talks between OpenAI and SoftBank are ongoing, and it is unclear who would make up the remaining $15-25bn. The round size and structure could still change.

Both firms are also seeking further funds for Stargate. Alongside their $38bn investment, Oracle and Abu Dhabi's MGX will put in a combined $7bn. The remaining $455bn could come in the form of debt financing.

SoftBank is currently looking to woo investment firms Apollo Global and Brookfield for further Stargate funding, Nikkei reports.

The Japanese telco and tech conglomerate continues to invest heavily in AI companies, despite its roughly $140bn debt burden.