Article 140 of the permanent Iraqi constitution adopted on 15 October 2005 provided that a referendum be held by the end of 2007 to determine the ultimate political fate of the province and city of Kirkuk (as well as the provinces of Nineveh, Diyala, and Salah al-Din), which the Kurds claimed should become part of the Kurdistan Regional Government (KRG) but which also consisted of many Arabs, Turkomans, and Christians. An earlier version of Article 140 had appeared in the Transnational Administrative Law (TAL) as Article 58. Due to an inability to agree on the specifics of such a referendum, Article 140 has not been implemented and as of this writing seems unlikely to be. This situation greatly frustrates the Kurds but is the result of the renewed power of the Iraqi Arabs as well as the continuing strength of Turkey, which fears that by annexing Kirkuk, the KRG would become strong enough to seek independence and then possibly divide Turkey by appealing to the ethnic Kurds in that state.
Historical Dictionary of the Kurds. Michael M. Gunter.