The SpaceX boss posted a series of posts on X in response to remarks made by Sean Duffy about the timeline for getting humans back to the moon

Sean Duffy, the Secretary of Transportation and acting administrator of NASA, appeared on CNBC on Monday to say that SpaceX had fallen behind in its effort to return Americans to the moon with the Artemis program. And SpaceX CEO Elon Musk was not happy about it.

While NASA has been planning to use SpaceX's Starship rocket system to land on the lunar surface, proposals will now be accepted from rivals as the US tries to return astronauts to the moon before China gets there.