"I will not sell any shares," Musk writes; he holds about 42 percent of the shares and almost 79 percent of the votes in SpaceX.
The post is a response to a claim from another X user.
SpaceX may file for an IPO as soon as Wednesday next week, Bloomberg reports, citing sources.
The owners reportedly want to raise $75 billion in the listing, valuing the company at more than $2 trillion (approximately SEK 18.9 trillion) - by far the largest listing of all time.
According to Bloomberg, SpaceX is aiming for June 12 as its first day of trading as a publicly traded company.
