OpenAI is currently in “a tough negotiation” with one of its biggest investors and partners, Microsoft, according to the Financial Times.

The AI startup recently announced a major change to its corporate restructuring plans — while it still aims to convert its business arm into a for-profit public benefit corporation, its nonprofit board will remain in control.

The FT says it spoke to multiple sources who describe Microsoft, which has invested $13 billion in OpenAI to date, as a key holdout needed to approve the restructuring.

While the crux of the negotiation is how much equity Microsoft will receive in the new for-profit entity, the companies are also reportedly renegotiating their broader contract, with Microsoft offering to give up some of its equity in exchange for access to OpenAI technology developed after the current 2030 cutoff.

Sources also told the FT that these negotiations are complicated by the increasingly competitive relationship between the two companies, as OpenAI’s enterprise business has grown and as it pursues its wildly ambitious Stargate infrastructure project.