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"Targeting ISIL's money will be a significant challenge given its clandestine financing sources," said Mark Dubowitz, a counterterrorism expert with the Foundation for Defense of Democracies.
"But since 9/11, Treasury's Terrorism and Financial Intelligence unit has deep experience and notable successes in tracking terrorist financing networks and uncovering and punishing [Persian] Gulf donors who have underwritten Sunni jihadism," he said.