Argo and Zero Dark Thirty scoop Writers Guild awards
CIA thriller Argo and Zero Dark Thirty have won the top screenplay honours from the Writers Guild of America.
The adapted screenplay award went to Chris Terrio for Ben Affleck's Iran hostage drama.
Mark Boal took the original screenplay prize for Kathryn Bigelow's film chronicling the manhunt for Osama Bin Laden.
Malik Bendjelloul won the documentary award for Searching for Sugar Man, about the 1970s musician Rodriguez.
The guild was the last of Hollywood's major trade unions to hand out awards before next Sunday's Oscars.
Argo has emerged as the best picture favourite at the Academy Awards, after scooping the top prize at the Baftas and Golden Globes, in addition to awards from the Directors Guild of America, the Screen Actors Guild and the Producers Guild of America.
"I've never actually won a call-your-name award before," Terrio said backstage after winning his award.
Prizes for television writing were also handed out, with Breaking Bad winning best drama series.
The writers of Louis claimed the prize for comedy series and Lena Dunham's Girls was named best new TV series.