The two men have long had a rivalry, and this isn't the first time the Microsoft cofounder has criticized Musk.

Gates calls out the ‘stunning’ reductions in USAID funding during an interview with The New York Times.

Bill Gates pledged on Thursday to give away almost his entire personal wealth in the next two decades and said the world's poorest would receive some $200 billion via his foundation at a time when governments worldwide are slashing international aid.