Elon Musk is planning to build a "self-growing city" on the moon

In a post on X - which he also owns - Musk wrote: "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 has previously told how SpaceX was aiming to colonise Mars.

But the focus has now shifted, partly because travel to the moon is possible every 10 days, whereas a jaunt to Mars is only possible every 26 months.

He added: "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."

Despite the shift in focus, the Tesla CEO has insisted SpaceX is still aiming to start building a city on the Red Planet "in about five to seven years".

He added: "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."

In 2020, Musk was "highly confident" SpaceX would be able to land humans on Mars by 2026.

Speaking on an award show webcast from Berlin, Germany, he said at the time: "If we get lucky, maybe four years.

"We want to send an uncrewed vehicle there in two years."

Last year, US President Donald Trump - who is friends with Musk - told how he wanted to plant an American flag on Mars.

Speaking to a joint session of Congress, he said: "We are going to conquer the vast frontiers of science, and we're going to lead humanity into space and plant the American flag on the planet Mars and even far beyond."