The documentary was made by David O Russell, who directed the 1999 black comedy 'Three Kings', which is set during the first Gulf War and stars Clooney alongside Mark Wahlberg, Ice Cube and Spike Jonze.
Iraqi refugees and veterans of the first Gulf War are interviewed in the documentary, which was to be featured on a special DVD release of the film and also shown with the film in a limited theatrical release.
Warner Bros spokeswoman Barbara Borgliatti told the New York Times today that the documentary was supposed to follow up the lives of the Iraqi extras who appeared in the film, but that was not what Russell had delivered.
"This came out to be a documentary that condemns, basically, war. This is supposed to be a special edition of 'Three Kings', not a polemic about war," Borgliatti said.
"Warner Bros does not think it's appropriate to attach this polemic to an entertainment piece. We don't think it's appropriate to marry these two things," she added.
With American opinion divided about the justification and outcome of the war in Iraq, studios have been very sensitive about releasing material that deals with the subject.
Michael Moore's box office hit 'Fahrenheit 9/11' saw a spat arise between distributor Miramax and parent company Disney, which was concerned about the film's highly critical stance on the Bush administration.
The film opened in the US in July, but some cinemas screening the film were threatened with boycotts by right-wing groups.
The New York Times reports that Russell is now trying to get his documentary screened independently before the November election, with political organisation MoveOn.org being mooted as a potential distributor.
Warner Brothers is said to have been concerned that releasing the documentary before the elections could breach Federal Election Commission regulations, even though it does not mention George W Bush nor his Democrat rival John Kerry.
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