In an unexpected billionaire feud, Bill Gates accused Elon Musk of contributing to the deaths of children after the U.S. government’s cuts to international aid.

Gates, who plans to donate his entire $200 billion fortune by 2045, expressed concern that Musk’s role in dismantling USAID’s funding could lead to millions of deaths due to lack of access to food, water, and healthcare.

Gates, who focuses on philanthropy through the Gates Foundation, said Musk’s actions would “kill the world’s poorest children.” Musk quickly denied the accusations, calling Gates a “huge liar” on social media.

The debate highlights the clash between Gates’ philanthropic approach and Musk’s reliance on innovation and free-market solutions.