Bill Gates criticized Elon Musk in a recent interview with BBC.

Gates was asked if he thinks Musk will join other wealthy donors in pledging to give away most of his wealth.

Gates said he believes Musk will eventually be a great philanthropist, but not at the moment.

Gates views the effort to go to Mars as a waste of money and not a good use of funds.

Gates thinks providing vaccines to people in need should be a higher priority than going to Mars.

Gates says it's expensive to go to Mars and measles vaccines can save lives for $1,000 per life saved.

Gates and Musk have had a history of being at odds with each other.

Musk declined Gates' offer to collaborate on philanthropic efforts to combat climate change.

Gates has praised Musk for his work with Tesla and SpaceX in past.

Gates says Musk should not be underestimated and he has the potential to improve Twitter.