Jeff Bezos-backed space company Blue Origin LLC is slated to launch its New Glenn rocket from Cape Canaveral, Florida on Sunday, a crucial test in the startup’s quest to challenge SpaceX.

Blue Origin has postponed the second flight of its New Glenn rocket, which was slated to send a pair of NASA spacecraft on the first step of their journey to Mars on Sunday afternoon.

Rescheduling could prove challenging given the US government shutdown.