Iraq crisis: Where will ISIS attack next?
14 June 2014 Last updated at 10:54 BST
US President Barack Obama has said he will take several days to decide what action to take over Iraq, but that no US troops will be deployed there.
Any US involvement "has to be joined by a serious and sincere effort by Iraq's leaders to set aside sectarian differences", he said.
In recent days Sunni insurgents have seized the cities of Mosul and Tikrit, and are moving closer to Baghdad.
Jim Muir gave his analysis on what ISIS's next move may be.