Iraq's Kurdish region will hold an independence referendum on Sept. 25, officials announced Wednesday.

The Kurds have been crucial to the U.S.-backed offensive against ISIS, which has seen the terrorist group lose most of its territory in Iraq. But there is stiff resistance from the Iraqi government and from Turkey to the idea of an independent Kurdish state.

What voters will be asked: Do you want an independent Kurdistan?

The oil question: An official said the proposed Kurdish state would include the oil-rich Kirkuk region, Reuters reports.