THE CIA thrillers Argo and Zero Dark Thirty have won top screenplay honours from the Writers Guild of America.
The guild's adapted screenplay award went to Chris Terrio for Argo – director Ben Affleck's tale of the CIA's daring masquerade as a Hollywood film crew, in an attempt to rescue six US diplomats from Iran during a hostage crisis.
Mark Boal won the prize for original screenplay for Zero Dark Thirty, director Kathryn Bigelow's chronicle of the CIA's manhunt for al-Qaeda leader Osama bin Laden.
Meanwhile, director Malik Bendjelloul won the documentary award for Searching For Sugar Man, his portrait of the acclaimed but largely forgotten 1970s musician Rodriguez.
The Writers Guild was the last of Hollywood's major trade unions to weigh in on the year's top films before next Sunday's Academy Awards.
Argo has emerged as the best- picture favourite for the Oscars after sweeping top prizes at earlier film honours, including the Golden Globes and awards from the Directors Guild of America, the Screen Actors Guild and the BAFTAs.