SoftBank, Toyota Motor Corp and Japanese auto-parts supplier Denso Corp are expected to invest a total of $1 billion as part of the deal, which could be announced in the next few days, the report said.
SoftBank closed its $8 billion investment in Uber in January 2018, which gave it a 16 percent stake in the ride-hailing company and made it the largest shareholder.
The Japanese technology investment fund also has investments in General Motors Co's self-driving car subsidiary Cruise. SoftBank and automaker Honda Motor Co have invested a total of $5 billion for acquiring separate minority stakes in Cruise.
Cruise has a value of more than $14 billion despite no significant revenue and a product not ready for commercial launch.
Uber is getting ready for its initial public offering (IPO) and filed for it last week.
Toyota and Denso declined to comment, while Uber and SoftBank did not respond to Reuters' requests for comment.
(Reporting by Sayanti Chakraborty and Vibhuti Sharma in Bengaluru; Editing by James Emmanuel)