"We're coming for you, Barack Obama," the group threatened, according to Elissa Slotkin, acting principal deputy undersecretary of defense for policy, in a story published by The Hill.
The group's insurgence inside the country has drawn the attention of U.S. officials who have called it "worse than al-Qaida."
"It is al-Qaida in its doctrine, ambition and, increasingly, in its threat to U.S. interests," Brett McGurk, a deputy assistant secretary of state, said in testimony during a House Foreign Affairs Committee hearing Wednesday.
McGurk was blunt in outlining the group's intent, calling it "no longer a terrorist organization. It is a full-blown army," the Hill reported.
Former Homeland Security head Tom Ridge also signaled the strength of the group and its capacity to create terror, adding that ISIS's threats had been on the intelligence community's radar for a long time with the ability to enter the United States unnoticed.
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"TheyÂ’ve got a lot of fighters who are from European countries that are visa waiver countries, which means all they have to do is shave their beards and look like normal, responsible civilians and walk into the United States of America without a visa," Ridge said. "ItÂ’s a real challenge for our intelligence community to identify them and get their names on a watch list."
Known as ISIL or ISIS, short for the Islamic State in Iraq and Syria, the group has powered throughout Iraq in recent weeks, commandeering the police force and entering homes where residents have gone missing at the hands of marauding posses.
Whole towns are under siege by ISIS forces, and the group has suggested it will overtake Baghdad, a threat that led Obama to deploy about 750 troops to the war-torn nation, The Washington Times reported.Christians are under particular assault by the Sunni terrorists, being told to convert or die, Al Jazeera reported. They have also been pressured to pay a tax, and those who have fled have been robbed at checkpoints by insurgents.
"There is not a single Christian family left in Mosul," Bashar Nasih Behnam, 52, told The Guardian.