Elon Musk.

Senator Bernie Sanders has responded to Tesla CEO Elon Musk's claim that he needs his vast wealth to fund interplanetary travel by telling him that "we need to focus on earth," and raise taxes on higher earners in order to tackle the "obscene" level of inequality in the US.

Following criticisms of the scale of his wealth, Musk tweeted on Sunday that "I am accumulating resources to help make life multiplanetary & extend the light of consciousness to the stars".

However, responding to the comments, Sanders tweeted that: "Space travel is an exciting idea, but right now we need to focus on Earth and create a progressive tax system so that children don't go hungry, people are not homeless and all Americans have healthcare."

He added: "The level of inequality in America is obscene and a threat to our democracy."

The progressive lawmaker was responding to Musk, one of the wealthiest people in the world, who claimed the previous day that he would use his fortune to fund space exploration after Sanders criticised his level of wealth.

Musk last week overtook Amazon CEO Jeff Bezos to become the world's richest person, according to Bloomberg's Billionaires Index, with an estimated fortune of $182 billion, thanks to a week-long Tesla stock rally.

Musk also runs the space exploration firm SpaceX and previously said he wants to send a million people to Mars by 2050. He said he was "highly confident" that he would send the first SpaceX Starship to land successfully on Mars by 2026 and predicted there will be "a lot of jobs" on Mars.

Musk's defense of his wealth came in response to a column by the outlet Clean Technica that criticised previous comments made by Sanders about Bezos and Musk's wealth.

"We are in a moment in American history where two guys [Musk and Bezos] own more wealth than the bottom 40 per cent of people in this country," Sanders said. "That level of greed and inequality is not only immoral. It is unsustainable."

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