Elon Musk said that SpaceX will focus on building a self-growing city on the moon first, then do the same on Mars.

"For those unaware, SpaceX has already shifted focus to building a self-growing city on the Moon, as we can potentially achieve that in less than 10 years, whereas Mars would take 20+ years," Musk posted on X on Sunday. "The mission of SpaceX remains the same: extend consciousness and life as we know it to the stars.

"It is only possible to travel to Mars when the planets align every 26 months (six month trip time), whereas we can launch to the Moon every 10 days (2 day trip time). This means we can iterate much faster to complete a Moon city than a Mars city. That said, SpaceX will also strive to build a Mars city and begin doing so in about 5 to 7 years, but the overriding priority is securing the future of civilization and the Moon is faster."

Musk's post follows a Wall Street Journal report on Friday, which said that SpaceX told investors it would prioritize a mission to the moon first and attempt a trip to Mars at a later date, aiming for March 2027 for an uncrewed lunar landing, according to Reuters.

The U.S. faces competition from China in its effort to return astronauts to the moon, where no humans have visited since the final U.S. Apollo mission in 1972.