By Jonny Dymond
BBC correspondent in Istanbul
The Turkish military has warned that continuing ethnic tension in the northern Iraqi city of Kirkuk could threaten Turkey's national security.
Since Saddam Hussein fell, Kurds have flocked back to their homeland
Gen Ilker Basbug, of the Turkish general staff, criticised the US for failing to tackle Kurdish paramilitary forces based in the far north of Iraq.
The area borders south-east Turkey, and both regions are predominantly Kurdish.
Turkey has warned repeatedly against an independent or autonomous Kurdish state breaking free of the rest of Iraq.
It believes that such a state might threaten Turkey's own territorial integrity.
Oil-rich Kirkuk is of particular interest to Turkey as it believes outright Kurdish control of the city would bring an autonomous Kurdistan a step closer.
As Gen Basbug made clear, Turkey believes that Kirkuk must remain a mixed city, with control shared between Kurds, Arabs and Turkmen.
Gen Basbug said that the current situation in Kirkuk could lead to civil war.
He also called on the US to make good its promise to tackle the Kurdish paramilitary Kongra-Gel, once known as the PKK.
The paramilitaries waged a bitter struggle against the Turkish state in the 1980s and 1990s. Around 5,000 members are believed to live in the mountains in the far north of Iraq.
Across the border in south-east Turkey, there has been a sharp rise in the number of clashes between Kongra-Gel members and members of the Turkish security forces in the past couple of months.