A new war is threatening Iraq just as the world believes the country is returning to peace. While violence is dropping in Baghdad and in the south of the country, Arabs and Kurds in the north are beginning to battle over territories in an arc of land stretching from Syria to Iranian border.

A renewal of the historic conflict between Arabs and Kurds in Iraq, which raged through most of the second half of the 20th century, would seriously destabilise the country as it begins to recover from the US occupation and the Sunni-Shia civil war of 2005-07.

Yet if the conflict develops into a full-scale war it will complicate President Barack Obama's plan to withdraw 142,000 US soldiers from Iraq over 16 months and redeploy many of them to the US military effort in Afghanistan.

In some respects, the Arab-Kurdish war has already started. Kurdish leaders say that in Nineveh province, Sunni Arab gunmen have killed 2,000 Kurds and 127,000 Kurds have turned into refugees over the past six years.