The Screen Actors Guild called the studios offer regressive
The largest union representing US actors has rejected the "last, best and final offer" from Hollywood's major studios for a new contract.
The rejection raises the possibility of further labour unrest in Hollywood.
The studios want the contract to start from when it is signed. But the Screen Actors Guild wants it to date from when the last one expired in June 2008.
The studios said they could not offer SAG a "better deal" than those agreed to in 2008 by other Hollywood unions.
"The (studios') last-minute, surprise demand for a new term of agreement... is regressive and damaging and clearly signals the employers' unwillingness" to negotiate a deal, SAG said in a statement.
By taking the start date back to 1 July 2008, the contract would expire at a similar time to those of the writers' and directors' guilds, thereby increasing the union's bargaining power in 2011.
The studios' organisation - the Alliance of Motion Picture and Television Producers - issued its own statement in response:
"We simply cannot offer SAG a better deal than the rest of the industry achieved under far better economic conditions than those now confronting our industry".
The threat of strike action has been hanging over Hollywood since the last contract with SAG ran out in June 2008.
The union, which has 120,000 members, had objected to plans to make one-off, not residual payments, to actors for made-for-internet shows.
Reports from the recent talks suggest progress has been made over how actors would be paid for work distributed on the internet.