600 More Troops to Iraq are What's Required to Take Mosul, Carter Says

Carter said the new troop level "is what we now foresee as required for the envelopment and seizure of Mosul," but they'll "continue to assess" that with Abadi.

"We're on schedule in terms of marshaling the forces there. So the force generation, which begins with training and arming and is a process that has moved along now consistently for many months; the movement, then, of those forces both Iraqi army and [Iraqi Counter Terrorism Service] forces, and also Peshmerga forces," he said.

"...We do not know what ISIL's plans will be for the defense of Mosul nor whether they'll be able to carry out whatever plans they have, whether their fighters will stick with them, whether they'll have morale to do that, whether the populous of Mosul will tolerate their continued presence in their city under those circumstances."

Carter emphasized that the U.S. is going to "continue to help the Iraqi security forces in whatever measure and manner they wish to consolidate the control over their country after they've re-captured this last major ISIL center."