"We do not think the referendum should happen in September," McGurk said on Thursday. "Right now [Daesh] is not finished and we have to be clear about that."
McGurk explained that the referendum held on such a fast time line would be destabilizing for Iraqi and Kurdish forces fighting against Daesh.
"[Daesh] are in Tal Afar just south of the Kurdistan region and Hawija just west of Kirkuk. The Hawija operation will be very complex and it will involve Iraqi Security Forces and Kurdish Pershmerga, so this is not the time to hold a referendum in this area."
Kurdistan Regional Government President Masoud Barzani met on June 7 with all the political parties in Kurdistan and they agreed on a September date for the referendum, according to published reports.