U.S. officials allege that energy mogul George Haswani acts as a middleman between the Islamic State, which controls much of Syria's oil and gas infrastructure, and the Syrian government. Mr. Haswani outlined a history of the gas project in a five-page letter sent a year ago to the New York-based Counter Extremism Project, a nonprofit that promotes international efforts to fight Islamic militancy. The organization’s chief executive, former U.S. diplomat Mark Wallace, wrote to the businessman last March with questions over the allegations of his role in funding the Islamic State.