Boeing on Saturday warned employees involved in its Space Launch System moon rocket program that it expected to lay off around 400 people.

Elon Musk, founder and CEO of SpaceX, has advocated for a Mars-first strategy and has previously called planned missions to the Moon a “distraction."

Boeing informed its employees working on NASA's Artemis program that it was preparing for as many as 400 layoffs connected to the giant rocket under development amid possible shakeups to the country's return-to-the-moon initiative, the company said.