Multiple private groups in Riyadh have made formal inquiries, the report added.
British billionaire Jim Ratcliffe, a life-long supporter of the club and founder of chemicals firm INEOS, is a likely bidder, along with US private equity firms and possibly Qatari investors, sources told Reuters.
A deal for the record 13-time English Premier League winners will likely exceed the biggest sports deal so far, the $5.2billion - including debt and investments - paid for Chelsea, the sources added.
Manchester United is the fourth richest soccer club in the world, according to analysis by Deloitte.
A small portion of Manchester United shares is listed in the United States with a market capitalisation of more than $4billion, as of Wednesday's close.
The club declined to comment on the matter.