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Retired General John Allen, the special presidential envoy for the global coalition against Islamic State, listens during a House Foreign Affairs Committee hearing in Washington, D.C., U.S., on Thursday, March 26, 2015. The U.S. and allies began airstrikes on the Iraqi city of Tikrit, supporting Iranian-backed Shiite militias seeking to expel Islamic State fighters from the area. Asked whether Iran could end up controlling Iraq, Allen said, 'I don't think that's going to be the case. In the end, Iraq is an Arab country.' Iranians, he said, 'are a different people.' Photographer: Andrew Harrer/Bloomberg via Getty Images

Retired General John Allen, the special presidential envoy for the global coalition against Islamic State, listens during a House Foreign Affairs Committee hearing in Washington, D.C., U.S., on Thursday, March 26, 2015. The U.S. and allies began airstrikes on the Iraqi city of Tikrit, supporting Iranian-backed Shiite militias seeking to expel Islamic State fighters from the area. Asked whether Iran could end up controlling Iraq, Allen said, 'I don't think that's going to be the case. In the end, Iraq is an Arab country.' Iranians, he said, 'are a different people.' Photographer: Andrew Harrer/Bloomberg via Getty Images