Hollywood screenwriters and producers have failed to resolve a contract dispute at last-ditch talks.
Writers have been leafleting the public to explain their grievances
The failure means the writers may stage a strike that could cripple production of many television programmes.
Studios have stockpiled scripts, but they will have no writers for comedy programmes that depend on topical gags.
The writers' union is seeking extra payments for their work when it is re-used on other platforms such as DVDs, the internet and mobile phones.
At present, they receive nothing extra if their work is featured in such formats.
The writers' current contract with the studios expired at 0001 local time (0701 GMT) with no replacement agreed and no new negotiations immediately scheduled.
Wednesday's negotiations started with the Writers' Guild of America (WGA) reportedly presenting a new set of proposals containing unspecified concessions and were attended by a federal mediator.
Late-night comedy shows may be among the first affected
But after eight hours of talks the studios issued a statement saying the writers' demand for a greater share of revenue from DVD sales constituted "a complete roadblock to any further progress".
The WGA should "take the necessary steps now to break this impasse", said the Alliance of Motion Picture and Television Producers.
But in its statement, the union disputed this version of events, saying the alliance had insisted writers not only accept the existing "hated DVD formula", but extend it to internet downloads.
"Every issue that matters to writers, including Internet reuse, original writing for new media, DVDs, and jurisdiction, has been ignored" in the bargaining, said the WGA. "This is completely unacceptable."
The WGA voted unanimously in favour of strike action two weeks ago, but it is unclear whether it will go ahead.
In the event of a strike, the studios are expected to resort to repeats, extended news programmes and reality TV shows.
However, late-night topical comedy shows - such as the Tonight Show with Jay Leno and the Daily Show with Jon Stewart - would be severely affected.
The last major WGA strike in 1988 lasted 22 weeks, delayed the start of the autumn TV season and cost the industry an estimated $500m.
The studios say higher royalties for writers on new media products would stifle growth at a time of increasing production costs, but the union accuses the studios of pleading poverty while earning healthy profits.