At the time, the ChatGPT-maker expected the deal negotiations to be completed in the coming weeks, people familiar with the plans said. But the talks haven’t progressed beyond the early stages, some of the people said.

Now, the two sides are rethinking the future of their partnership, some of the people said. The latest discussions, they said, include an equity investment of tens of billions of dollars as part of OpenAI’s current funding round. 

Nvidia Chief Executive Jensen Huang has privately emphasized to industry associates in recent months that the original $100 billion agreement was nonbinding and not finalized, people familiar with the matter said. He has also privately criticized what he has described as a lack of discipline in OpenAI’s business approach and expressed concern about the competition it faces from the likes of Google and Anthropic, some of the people said.

“Our teams are actively working through details of our partnership. NVIDIA technology has underpinned our breakthroughs from the start, powers our systems today, and will remain central as we scale what comes next,” an OpenAI spokesman said. 

An Nvidia spokeswoman said that Nvidia has been OpenAI’s preferred partner for the past 10 years and it looked forward to continuing working with the company.

OpenAI is laying the foundation to go public by the end of 2026, and has spent much of the past year racing to secure large amounts of computing capacity to help power OpenAI’s future products and growth. The stalled Nvidia pact is a blow to this effort and shows how CEO Sam Altman’s penchant for announcing flashy big-ticket deals carries the potential to backfire if the terms have yet to be finalized.

In a joint announcement unveiling the September deal with Altman and OpenAI President Greg Brockman, Huang called the deal “the largest computing project in history.” Nvidia’s stock rose by nearly 4% on the news, pushing its market value to almost $4.5 trillion. As part of the deal, Nvidia discussed guaranteeing some of the loans OpenAI planned to take out to build its own data centers, The Wall Street Journal previously reported.

OpenAI went on to sign a string of other agreements with chip and cloud companies that helped fuel a global stock-market rally. But investors have since grown jittery about the startup’s ability to pay for these deals, leading to a selloff in some tech stocks tied to OpenAI. Altman has said that the deals put the startup on the hook for $1.4 trillion in computing commitments—more than 100 times the revenue it was on pace to generate last year.

OpenAI executives say the total commitments are lower after accounting for overlap in some of the deals, and that the agreements will take place over a long period.

Much of the recent concern about OpenAI has come from the success of Google’s Gemini app, which slowed ChatGPT’s growth and led OpenAI to declare a code red. Anthropic is also putting pressure on OpenAI thanks to its popular AI coding agent, called Claude Code. Nvidia said in November that it was committing to invest up to $10 billion into Anthropic.

In a November filing, Nvidia said there was no assurance that it would “enter into definitive agreements with respect to the OpenAI opportunity or other potential investments, or that any investment will be completed on expected terms, if at all.”

At a UBS conference in Scottsdale, Ariz., the following month, Nvidia CFO Colette Kress said that the company hadn’t completed a definitive agreement with OpenAI.

Huang has indicated to associates that he still believes it is crucially important to provide OpenAI with financial support in one form or another, in part because OpenAI is one of the chip designer’s largest customers, people familiar with the matter said. If OpenAI were to fall behind other AI developers, it could dent Nvidia’s sales.

Anthropic relies heavily on a combination of chips designed by Amazon Web Services known as Trainium, as well as Google’s in-house designed TPU processors, to train its AI models. Google largely uses its TPUs to train Gemini. Both chips represent major competitive threats to Nvidia’s bestselling products, known as graphics processing units, or GPUs.

News Corp, owner of The Wall Street Journal, has a content-licensing partnership with OpenAI.

Write to Berber Jin at berber.jin@wsj.com and Robbie Whelan at robbie.whelan@wsj.com