Steve Clemons of the New America Foundation believes that if the death toll surges, the Obama administration will be open to criticism from political opponents.

"Sure, Obama will be attacked by those on the right, some on the left, abandoning people, are we doing enough to help restore civil society? Are we neglecting responsibilities we set up for ourselves?"

But Clemons says most Americans now are more than happy to allow the Iraqis to take on the burden of security for themselves: "The equilibrium inside Iraq is going to change as those US forces pull back," he says.

"There's likely to be more violence, that's to be expected; but the sovereign government (of Iraq) wants [the withdrawl] to happen, and are calling for a national holiday to celebrate the removal of US forces from those cities.

"So Obama … has the cover of the Iraqi government saying we want to take over these responsibilities on security."