SoftBank is seeking to borrow more than $11bn in what would be one of the largest high-yield bond deals ever sold to investors, as Masayoshi Son’s tech giant looks to fund its multibillion investment in OpenAI.

The Japanese company is marketing $10bn and €1bn of bonds to credit investors, as part of a deal that will fund the third tranche of an investment in OpenAI expected to close next month, according to terms shown to investors. The bonds are expected to be priced on Thursday.

SoftBank’s latest transaction adds to a debt pile already amassed by one of the world’s largest investors in AI, which has borrowed billions of dollars to fuel bets on OpenAI and the wider AI boom. Earlier this year the firm struck an agreement to borrow up to $40bn in bridge loans from lenders including Japanese bank Mizuho to fund investments in OpenAI.

OpenAI expects to burn through almost $280bn by the end of 2030 as it invests aggressively to expand its access to computing power. Its ability to secure funding is critical to agreements with tech groups including chipmaker Nvidia and Oracle. SoftBank’s data centre business is also dependent on contracts with OpenAI for future revenues.