SpaceX is planning to sell existing shares starting Tuesday to a select group of buyers and there is speculation Elon Musk is a seller, The Post has learned.

Musk has been trying to raise more money for his $44 billion Twitter bid and is not only having a difficult time but finding it expensive, sources close to the situation said.

The billionaire could sell SpaceX shares instead to help fund the acquisition. As of August, the Tesla tycoon owned 44 percent of the SpaceX shares, according to federal filings.