NASA and Pentagon officials moved swiftly this past week to urge competitors to Elon Musk’s SpaceX to more quickly develop alternative rockets and spacecraft after President Donald Trump threatened to cancel Space X’s contracts and Musk’s defiant response.

The U.S. government relies on SpaceX to support NASA and other agencies, and the company has received more $20 billion in federal contracts for it. As Musk and Trump threaten to cut ties, here’s what that would mean for the U.