A Darkening In the North.

Byline: Rajan Menon (Menon is a professor of international relations at Lehigh University and a fellow at the New America Foundation.)

Iraq's kurdish north has offered a heartening contrast to an otherwise blood-soaked country. Its polity works; its economy thrives. But the reports last week of a Turkish military incursion, in pursuit of Kurdish rebels, is an eruption of only one of three steadily deepening problems that could combine to worsen the Bush administration's predicament in Iraq.

The first is the dispute over Kirkuk, capital of At-Tamim province. The city and its environs contain some 10 billion of Iraq's 112 billion barrels in proven oil reserves. Saddam Hussein expelled thousands of Kurds as well as Turkomans and Christians from the Kirkuk region in the 1980s and 1990s, replacing them with Arabs, mainly Shia from the south, themselves victims of his repression. With Saddam gone, roughly 350,000 Kurds moved back (some original residents, others not) with active support from the Kurdistan Regional Government (KRG). Thousands of Arabs fled, alleging threats and attacks by Kurdish groups. The influx also displaced Turkomans, but they continue to stake their own claim to Kirkuk, supported by Turkey.

Iraq's Constitution requires a referendum on Kirkuk's future status by the end of this year, and as the deadline nears, the carnage increases. Car bombs, sectarian murders (fanned by Al Qaeda in Mesopotamia), and expulsions abound. The vote will make matters worse. The run-up will almost certainly be marred by violence, and Arabs and Turkomans will reject a Kurdish victory. But the Kurds threaten to leave Iraq's government if it is postponed, as the Iraq Study Group recommended. Kirkuk looks like the Gordian knot that can't be cut.

The second problem involves Mosul, Iraq's third largest city and capital of Nineveh province, which lies just west of Iraqi Kurdistan. Sunni militias and Al Qaeda have been targeting Mosul's Kurds, who are fleeing to Kurdistan or areas near its border. Kurdish militias have retaliated, but have not been drawn into a full-blown civil war. That could change, which is what Al Qaeda wants; a new front would further stretch American forces.

Nineveh's tensions also stem from the underrepresentation of Sunnis, who boycotted the 2005 provincial elections. Some observers recommend fresh elections to redress the imbalance, but absent a minimum ...