Major General Stanley McChrystal, of the US Joint Chiefs of Staff, said the state of the four Republican Guard was "very confused".

"We know they have moved parts of those divisions around and in fact they have become intermixed with other elements on the battlefield," McChrystal told a Pentagon news briefing.

"We know that overall each of those remaining for divisions have been significantly attrited to this point, significantly degraded," he said. "Those remaining four are nothing like they were when they started the battle."

The other two divisions -- the Medina and Baghdad division -- which formed the main defensive line south of Baghadad were missing "essentially in their entirety," he said.

WAR.WIRE