Billionaire inventor and entrepreneur Elon Musk said he is willing to sell some of his Tesla stock if the United Nations can back its claim that it would only take $6 billion to solve world hunger.

Musk published a tweet challenging the UN to prove its claim that the World Food Program would only need $6 billion to solve global hunger. The amount is roughly equivalent to about 2% of Musk's current net worth.

The world's richest man said in his tweet that if the WFP can publicly disclose how it would use the funds to solve world hunger, he would pay for it himself. Musk also demanded that the accounting must be made open source so the public can track where and how the money will be spent.

 Musk's tweets are in response to David Beasley, the Executive Director of the UN World Food Program. Beasley had called on the world's billionaires to step up and help. He said it would only take $6 billion to help the 42 million people who are now dying of starvation.

"Just $6 billion to help 42 million people that are literally going to die if we don't reach them. It's not complicated," Beasley said.

Before his latest statement, Beasley had previously challenged Musk and Amazon's co-founder to donate some of their fortunes to help solve the world hunger issue. Beasley published a post earlier in the month congratulating Musk for overtaking Bezos as the world's richest man. He also specifically mentioned Musk's net worth of $221 billion, seemingly indicating that $6 billion would be a drop in the bucket for him.

Musk's net worth has risen to more than $300 billion since Beasley's first tweet. The $6 billion demanded by Beasley would be just 2% of Musk's total net worth.

Tesla recently also joined a small club of companies valued at more than $1 trillion last week. Musk is now worth almost $100 billion more than Bezos, now the world's second-richest man.

Last week, Microsoft reclaimed its title as the world's most valuable corporation, with a market capitalization of $2.46 trillion, after Apple's market value fell by almost 4% to $2.41 trillion due to a share price decline.