Dana Perrino, White House Spokesperson, held a press conference in Crawford TX on August 15th.
Q "Dana, there's a report out today that the September Iraq report will be written by the White House, and not by Ambassador Crocker and General Petraeus. Is that accurate?"
MS. PERINO: "Well, let me remind you of a couple of things. The Congress asked for these reports from the President; they asked for the President to report to the Congress. And so the July 15th report will be no different to the September 15th report, in terms of how that works. And the President has said that he's going to take the recommendations from General Petraeus and Ambassador Crocker, and then he will consult further before deciding on any possible next course of action."
Not entirely clear what she means, but this is a clear step-down from "I know a lot of people talk about 'the Petraeus report,' in fact, you have a report that is a joint report by General Petraeus and Ambassador Crocker." Now the two of them are just going to be making "recommendations" that Bush will then consider, along with many other inputs. I would especially note: "[Congress] asked for the President to report to the Congress." Not "Congress asked for General Petraeus to report..."
Horse's Mouth has more on the story, plus numerous quotes indicating that the report would be a joint Petraeus-Crocker production.