LOS ANGELES — Amid an emerging rivalry between traditional pay TV operators and rising star Netflix Inc., CBS Corp.'s Showtime pay TV service confirmed Wednesday that back seasons of current original series such as "Dexter" and "Californication" will not be available on Netflix's streaming service as of this summer.

LOS ANGELES — Amid an emerging rivalry between traditional pay TV operators and rising star Netflix Inc., CBS Corp.'s Showtime pay TV service confirmed Wednesday that back seasons of current original series such as "Dexter" and "Californication" will not be available on Netflix's streaming service as of this summer.

Instead, CBS will offer them to subscribers who pay for Showtime through Comcast Corp. on Comcast's Xfinity TV platform.

The deal was in place since February, but news of these details broke this week after Netflix announced it was buying the right to debut the series "House of Cards" from executive producer and Ashland High School graduate David Fincher.

Debuting an original series on its service makes Netflix even more of a direct rival to pay TV channels such as Showtime and HBO. Netflix had 20.2 million subscribers in the U.S. at the end of December, compared with just under 20 million for Showtime and HBO's estimated 28 million.

Showtime originals that have stopped airing on TV, including "The Tudors" and "Sleeper Cell," will continue to be available for streaming on Netflix.

CBS and Netflix announced a new two-year deal last month that allows older shows that are not generating new original episodes to be run on Netflix's streaming service, including "Medium," "Frasier" and "Cheers."

The deal followed a 10-year pact that CBS cut with Comcast in August that allowed for CBS and Showtime shows to be played on Comcast's Xfinity TV platform, which can be accessed on computers and iPad tablets.

CBS is seeking to maximize the money it can receive from Netflix from older content, while encouraging consumers to pay separately for new original shows on Showtime.

Other companies, such as Time Warner Inc.'s HBO have shunned Netflix entirely. HBO offers its service online for no extra charge to its pay TV subscribers.

Netflix meanwhile has been spending more to acquire the rights to TV shows and movies that it can stream to customers to wean them from ordering DVDs in the mail in an effort to reduce postage costs.