With his many years in Texas, Mr. Hitto may seem like an unusual selection to lead a government struggling to establish street credibility with rebels — or an uprising facing allegations from Mr. Assad’s supporters that it is an American creation.

But he said he could not resist getting involved, especially after his son Obaida, 25, sneaked off to Syria and joined rebel fighters to shoot videos, deliver humanitarian aid and spread word of their struggle.

Mr. Hitto and his wife, Suzanne, an American schoolteacher, have four children, all born in the United States, where Mr. Hitto advocated for Muslim Americans after 9/11 as a representative of the Council on American-Islamic Relations.

He traveled to the Middle East last fall to learn more and never went back. “I have a career back home that I’m in the process of destroying,” he said jovially over lunch recently in Istanbul.

In his role heading the humanitarian aid arm of the coalition under Suhair Atassi, a coalition vice president and respected activist from Damascus, Mr. Hitto quickly came into close contact with American and other foreign officials. Frustrated with what he saw as anemic and disorganized international efforts to aid displaced Syrians, he hired internationally known aid consultants to do a survey that found that the number of needy people in six Syrian provinces was more than 50 percent higher than United Nations estimates.

He described himself as a zealous but diplomatic advocate trying to push international donors to give the coalition a bigger role in the delivery of aid. “As an American,” he said, he wanted the United States to do more to support the rebels.

Born in Damascus, Mr. Hitto left Syria in the early 1980s and received an M.B.A. at Indiana Wesleyan University. He is of Kurdish descent, which the council may have seen as a plus since it has been criticized for not reaching out more to Syria’s minorities.