The Big Bang Theory contract talks have officially delayed production on the CBS hit comedy.

Stars Jim Parsons, Johnny Galecki, Kaley Cuoco, Simon Helberg and Kunal Nayyar have not yet reached a new deal with studio Warner Bros. Television, The Hollywood Reporter has learned, with the cast officially not returning to work on season eight.

"Due to ongoing contract negotiations, production on The Big Bang Theory &mdash which was originally scheduled to begin today &mdash has been postponed," WBTV said in a statement Wednesday. The first table read of the season was scheduled to take place today. It's unclear just how long production will be delayed as the cast and studio remain at an impasse on a new deal. The move comes as a surprise to the studio, which previously was not expecting there to be a work stoppage and the cast to arrive back at work Wednesday, with our without a contract.

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Emmy winner Parsons, Galecki and Cuoco are negotiating together and seeking big salary increases. Sources told THR in September that the trio, who currently earn $325,000 per episode, are seeking up to $1 million per half-hour with a cut of the show's back-end. Helberg and Nayyar are negotiating together and are also seeking hefty raises. Co-stars Mayim Bialik and Melissa Rauch previously inked new deals with WBTV, with both securing big raises.

The three-season renewal gives the cast, renegotiating new deals since September, considerable leverage &mdash especially considering Big Bang is TV's No. 1 comedy among total viewers, a metric it has held since the 2010-11 season. The season seven regularly topped 20 million viewers per week, up 4 percent year-over-year, with an impressive 6.1 rating among the advertiser-coveted adults 18-49 demographic. The show is also a hit in syndication on TBS, with repeats often topping some of the Big Four broadcast networks' original fare. Big Bang is again nominated for best comedy series, but the series has yet to take home that trophy.

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The series is a key part of CBS' fall roll-out. The network will use a full hour of Big Bang Theory on Mondays to help launch rookie drama Scorpion at 9 p.m. before it moves to Thursdays after the network's newly secured NFL programming concludes. It will then anchor the night again as CBS uses it to propel sophomore comedy The Millers.

The cast was a no-show this past weekend at San Diego Comic-Con, where for the second year in a row, the panel consisted of writers behind the series. Last year, Galecki made a surprise appearance with Rauch moderating. Parsons was at Comic-Con the day before the show's panel to DreamWorks Animation's Penguins of Madagascar, in which he has a voice role. There was no mention of the contract talks during the hourlong panel in San Diego.

Meanwhile, showrunner Steve Molaro has a three-year overall deal (his first) with WBTV, and co-creator/EP Chuck Lorre is also under contract with the studio. Securing Big Bang Theory's future was a top priority for CBS, which last season bade farewell to Monday staple How I Met Your Mother. CBS recently scored rights to Thursday night NFL games, pushing Big Bang Theory to Mondays for the first few weeks of season eight, before it returns to Thursdays.

For his part, Lorre didn't see the contract negotiations to be a problem, though that opinion may likely have changed now that production has been delayed. "There are people at Warner Bros. Television and people representing the actors who have done this before," he told THR this month. "This will work itself out. I think it's great; I want them all to be crazy wealthy because nobody deserves it more than this cast. It'll work out."

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The cast's decision to delay production comes after Modern Family co-creator/EP Christopher Lloyd staged a walk-out before &mdash missing the first week of work in the writers' room &mdash until he had reached a new deal with studio 20th Century Fox Television. The Emmy-winning comedy's cast also had a well-documented and contentious contract renegotiation in 2012 that threatened to delay production that concluded with the six adult actors earning major pay increases.

Email: Lesley.Goldberg@THR.com

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