Iraq yesterday said it had "regained the initiative" against militants who seized vast swathes of territory, as former UN mediator Lakhdar Brahimi blamed the crisis on global neglect of Syria's civil war.
Washington responded to the sweeping unrest by deploying an aircraft carrier group to the Gulf, but Iran has warned against foreign military intervention in its Shia neighbour, voicing confidence that Baghdad can repel the onslaught.
The USS George HW Bush, which carries dozens of fighter jets, is heading for the Gulf, accompanied by two more warships.
But the US says no US troops will be deployed on the ground in Iraq and Secretary of State John Kerry has repeated American demands for Iraqi leaders to put aside their differences.
The militants, spearheaded by the powerful Islamic State of Iraq and the Levant (ISIL) jihadist group, have overrun all of one province and chunks of three more since launching their offensive late Monday.
Security forces have generally performed poorly, with some abandoning vehicles and positions and discarding their uniforms, though they seem to be recovering from the initial onslaught and have started to regain ground.
Iraqi commanders have said their forces were now starting to repel the militants, and that soldiers had recaptured two towns north of Baghdad.
Officials added that security forces and tribal fighters repelled a militant assault in the strategic town of Tal Afar, which lies near the Syrian border and provides a critical corridor for militants to access conflict-hit Syria.
Iran yesterday warned that "any foreign military intervention in Iraq" would only complicate the crisis, voicing confidence that Baghdad "has the capacity and necessary preparations for the fight against terrorism". Iran earlier extended its helping hand ti Baghdad on repelling the militants.
The situation on the ground has been further complicated as forces from the autonomous Kurdish region have made territorial advances.
A senior official said Sunday that Kurdish peshmerga forces had taken control of one of two official border crossings with Syria earlier in the week. Kurdish forces have also seized the disputed ethnically mixed northern city of Kirkuk and surrounding areas, as well as other territory.