Tech leaders gathered at the White House this week to announce an ambitious new joint venture named the Stargate Project aimed at building new AI data centers in the U.S. The effort promises investments of $100 billion in the first year, and $500 billion over four years.

But details remain sparse.

SoftBank CEO Masayoshi Son will handle the financing, CEO Sam Altman of OpenAI will contribute his overall AI expertise, and Oracle executive chairman Larry Ellison will oversee the buildout. All three joined President Trump on Tuesday for the Stargate announcement.

MGX, a new AI investment firm in the United Arab Emirates with ties to the government there, will be a financing partner. Microsoft, Nvidia, and Softbank-owned Arm Holdings were named as technology partners.

There are several unanswered questions about the project, the most important being where the money is going to come from. SoftBank has about $38 billion in cash and short-term investments on its books, and $80 billion in long-term debt. The firm raised $100 billion for its Vision Fund venture capital fund, but struggled with a follow-up Vision Fund 2. Softbank's stake in Arm was worth over $140 billion as of Wednesday, and it could choose to sell shares to help finance Stargate.

Oracle has about $11 billion cash to go with $80 billion in debt. OpenAI is a start-up, still dependent on investor cash. It last raised $6.6 billion in October.

MGX may shoulder much of the financial burden, but it isn't clear what resources it can muster. MGX has three current investments, according to FactSet: OpenAI, Elon Musk's xAI, and another richly valued start-up, Databricks.

Mubadala, the U.A.E. sovereign-wealth fund, is an MGX investor. According to its website, Mubadala has about $300 billion of assets under management, suggesting Stargate would be a big lift, even for a large sovereign-wealth fund.

MGX also lists BlackRock, Silver Lake, Bain Capital and Vista Equity Partners as partners, among others.

Those are rich pockets, but $500 billion rich? We don't really know, and the Stargate partners aren't providing information.

SoftBank wouldn't comment to Barron's on the sources of Stargate funding. Nvidia and Arm offered general support for the initiative in their replies, but didn't clarify their roles in the partnership. OpenAI's own press release announcing the project didn't offer financing details.

Elon Musk quickly cast doubt on the whole initiative. "They don't actually have the money," Musk, a key Donald Trump ally, wrote on X. "SoftBank has well under $10B secured. I have that on good authority."

OpenAI CEO Sam Altman defended Stargate's funding in a social media post: "Wrong, as you surely know," he said in a reply to Musk on X. "This is great for the country. I realize what is great for the country isn't always what's optimal for your companies."

On Wednesday Arm CEO Rene Haas didn't provide details on financing, but told CNBC: "I would say rest assured that you would not have the individuals you saw yesterday and the president all together with such an announcement if there wasn't a lot of backing from a financial standpoint."

The debate and questions about funding highlight the significance of the expenditures and the complex nature of AI model building and deployment, and the infrastructure needed to support it.

For a sense of Stargate's proposed scale, Microsoft offers a good comparison. Microsoft is projecting $80 billion in capital expenditures in fiscal 2025, ending June, an 80% increase from 2024, which was a 58% rise from the year before that. Stargate wants to ramp from nothing to $100 billion, 25% larger than Microsoft's planned outlay -- all in one year. It's a big ask when considering Microsoft had $73 billion in annual free cash flow, and Stargate currently has none.

Microsoft, Nvidia, and Arm were left out of the equity discussion, suggesting their balance sheets won't contribute to the effort.

Microsoft has been OpenAI's biggest investor. Its Azure cloud is the home to OpenAI's signature ChatGPT service.

The new dynamic suggests bigger AI ambitions for both Microsoft and OpenAI.

"It is entirely plausible that the Stargate news was not forced on Microsoft, but that Microsoft viewed exclusively financing OpenAI no longer made sense from a risk and capital allocation standpoint," said UBS analyst Karl Keirstead in a note to clients. "Put another way, OpenAI's massive scale ambitions...may have been running up against Microsoft's desire to exclusively serve them."

Microsoft referred Barron's to a Tuesday blog post that briefly alluded to Stargate, but went on to redefine its close relationship with OpenAI. Most of their agreement through 2030 remains, the blog post said, but Microsoft's Azure cloud platform will no longer have exclusivity on new OpenAI computing demand, though it retains the right of first refusal on new cloud business.

While the partnership remains, there are cracks forming. They're likely to reverberate across the tech landscape.