Some of the movies for sale will come from Comcast-owned Universal Pictures, including this year's hit's "Fast & Furious 6" and "Despicable Me 2," according to one of the sources.
(Read more: Comcast's profit beats Street on cable, 'Despicable Me 2')
A Comcast spokeswoman declined to comment.
Now, Comcast and other cable operators offer on-demand movies for free viewing or rental to watch during a specific time period. Another pay TV operator, Verizon's fiber-based Fios service, sells and rents films digitally.
Movie studio executives are looking to boost digital sales as customers move away from purchases of traditional DVDs, cutting a lucrative source of revenue.
Through the first nine months of 2013, sales of packaged goods including DVD and Blu-ray discs dropped 7 percent from a year earlier to $5 billion, according to the industry-backed Digital Entertainment Group.
At the same time, digital sales reached $764.5 million, a 48.9 percent jump from a year earlier.
Spokespeople at Hollywood studios, including 20th Century Fox, Viacom's Paramount Pictures and Lions Gate Entertainment, declined to comment. A spokesman for Time Warner's Warner Bros. referred questions to Comcast. A Walt Disney Co spokeswoman had no immediate comment.
Movie sales through Comcast would give studios a chance to reach the roughly 20 million households that subscribe to the company's digital service.
Some studios including "Hunger Games" producer Lions Gate have offered certain titles for sale in digital formats before physical DVDs, a move to entice consumers to embrace online technology for watching films.
Last week, Lions Gate CEO Jon Feltheimer told Wall Street analysts he was expecting at least one major pay TV operator, which he did not name, to announce in the coming weeks that it would offer digital movie sales.
"When that happens, it's really going to open up amazing opportunities," Feltheimer said on a conference call.