Billionaire Elon Musk's SpaceX could become the most valuable startup in the U.S. as its valuation rose to more than $125 billion as a result of ongoing secondary market sales of shares, Reuters reported, citing sources.

The stock, which sells for about $72, has jumped in value from last October, when SpaceX shares were selling for $56.

In the capital-intensive business, SpaceX raised $337.4 million in December and $1.16 billion in equity financing last April, according to regulatory filings.

The company competes with former Amazon.com CEO Jeff Bezos' space venture Blue Origin and billionaire Richard Branson's Virgin Galactic in a growing constellation of commercial space ventures.

SpaceX has already launched numerous cargo and astronauts to the International Space Station for NASA, including 19 launches this year alone.