He said he resigned so he could “work with more freedom unavailable to me within the official position of the organization.”
Mr. al-Khatib’s frustration with international community was evident in February when he expressed a reluctance to attend a Friends of Syria conference in Rome. He eventually did so after pleas from Western officials, including Mr. Kerry.
“We view this as a continuum,” he said. “It’s not about one person It’s about an opposition that is bigger than one person.”
Mr. al-Khatib had often expressed his wish to step down, but was urged by supporters within the opposition coalition to complete his term in office, which ends in May, or at least stay for the Arab League summit in the Qatari capital, Doha, this week.
Opposition leaders will ask Mr. al-Khatib to stay on, but in the event that he insists on his resignation, one of the coalition’s three vice presidents will be named acting president until a fresh election is held, Mr. Ghadbian said in a phone interview.
The opposition suffered a second setback when the head of its military branch, Gen. Salim Idris, refused to recognize the coalition’s new prime minister. U.S.-educated Ghassan Hitto was elected last week to lead the opposition’s interim government.
While the opposition has struggled to remain a cohesive force, the Assad regime has shown no signs of crumbling.
Last week, the regime and opposition accused each other of using chemical weapons.
Syrian opposition leaders said the regime had attacked Khan al-Assal, north of Aleppo; al-Otaiba, near Damascus; and the Baba Amr neighborhood of Homs city, with Scud missiles carrying the chemical weapons. They said 26 people had been killed and hundreds of others wounded in the attacks.
U.S. officials say they have no evidence that chemical weapons were in fact used. The United Nations in investigating the incident.
President Obama has said that the Assad regime will have crossed a “red line” if it uses chemical weapons. The administration has said this violation would result in serious consequences, but has not said what those might be.