Elon Musk and OpenAI CEO Sam Altman are fighting on X about Stargate, the infrastructure project to build data centers for OpenAI in the U.S.

Elon Musk claimed overnight Tuesday that tech giants OpenAI, Oracle and Softbank don’t have enough money to fulfill their high-profile pledge to invest $500 billion in U.S. artificial intelligence infrastructure.

It’s the latest clash in a feud between the two tech billionaires that started on OpenAI’s board and is now testing Musk’s influence with the new president.