U.S. allies signaled their readiness to boost efforts to fight Islamic State under a coalition formed by President Barack Obama as the beheading of a British aid worker sparked further outrage.
While no Arab states have publicly committed to military action, several have told the U.S. privately they are willing to join in airstrikes in Iraq and in Syria, said a U.S. State Department official who spoke on the condition of anonymity.
U.K. Prime Minister David Cameron vowed to confront the militants with "iron determination."