Mounting casualties among US troops in Iraq - including more than 20 marines killed in the Euphrates valley last week - are dominating headlines in the US. Insurgent attacks are becoming more sophisticated in their range and power. American commanders, who after two years still have no clear picture of their enemy, talk as though they were wrestling with phantoms. The US air strikes pounding western Iraq will not make them more visible.

But the far greater slaughter of Iraqis is in danger of being overlooked - as is the fact that this carnage already has the contours of a sectarian war that could envelop the region.