The Washington Post’s Liz Sly and David Ignatius look back at the bloody Syrian civil war--thousands killed, a country in ruins and borders breached by a tide of refugees. What will the future hold for the Syrian people and the al-Assad regime, and how does the U.S. fit into that picture? (Jason Aldag/The Washington Post)

Syria’s opposition coalition was on the verge of collapse Sunday after its president resigned and rebel fighters rejected its choice to head an interim government, leaving a U.S.-backed effort to forge a united front against President Bashar al-Assad in tatters.

The resignation of Moaz al-Khatib, a moderate Sunni preacher who heads the Syrian Opposition Coalition, climaxed a bitter internal fight over a range of issues, from the appointment of an interim government to a proposal by Khatib to launch negotiations with the Syrian regime.

His departure plunged the opposition into disarray at a time when the United States and its Western allies are stepping up their support for moderates opposed to Assad’s regime. Khatib’s coalition was expected to play a key role in identifying the recipients and channeling the assistance.

The coalition later issued a statement saying that its members had rejected Khatib’s resignation and had asked him to continue in a “management” capacity, leaving his status unclear. Though Khatib’s suggestion earlier this year that the opposition should negotiate with Assad’s regime met with fierce resistance from other coalition members, he is widely liked by many Syrians inside the country who desperately want to see an end to the violence.

There nonetheless seems to be little doubt that an initiative launched last fall in the Qatari capital, Doha, to create an inclusive and representative opposition body is falling apart, said Amr al-Azm, a history professor at Shawnee State University in Ohio who is Syrian and supports the opposition.

“The coalition is on verge of disintegrating,” he said. “It’s a big mess.”

The trigger for Khatib’s departure was the selection last week of Ghassan Hitto, a relatively unknown Syrian-born U.S. citizen, to head a proposed interim government. Khatib and his supporters had opposed the creation of an interim government at this time, as had the United States, whose diplomats argued against the move on the grounds that it created an unnecessarily divisive distraction from the goal of bringing down Assad’s regime, according to Syrian opposition members.

Hitto’s candidacy was backed, however, by the Syrian branch of the Muslim Brotherhood, and the push to install him as Syria’s first opposition prime minister was widely seen as an effort by the Brotherhood to claw back some of the influence lost when the original Syrian opposition body, the Syrian National Council, was absorbed into the wider Syrian coalition.

A dozen members last week suspended their membership in the coalition to protest Hitto’s appointment, and on Saturday, the defected general who heads the Supreme Military Council of the mainstream Free Syrian Army also rejected the choice, saying the rebels would accept only a “consensus” candidate for the job.

“We unequivocally declare that the Free Syrian Army, in all of its formations . . . conditions its support and cooperation on the achievement of a political agreement on the name of a prime minister,” Gen. Salim Idriss said in a videotaped statement.

Khatib’s resignation came hours after Qatar, which has close ties to the Brotherhood and also supported Hitto’s appointment, formally invited Hitto to represent Syria at an Arab League summit in Doha next week. Khatib referred only obliquely to the furor over Hitto’s appointment, saying he had resigned “so that I can work freely,” something that is not possible “within the official institutions.”

He also hinted at his frustration with the international community, which has failed to offer wholehearted support to the Syrian revolution even as individual countries compete to secure influence over the different factions opposing Assad’s regime.

“Who is ready to obey, [those countries] will support him,” he said. “And those who refuse to obey endure starvation and siege.”

The upheaval is indeed as much an indictment of splits within the international community over whom to support within the opposition as it is of the divisions among Syrians themselves, said Salman Shaikh, director of the Brookings Doha Center in Qatar. With the United States, Qatar, Saudi Arabia and others each favoring different factions, it is hardly surprising, he said, that the opposition is failing to unite.

“We cannot continue trying to forge these kind of coalitions with these kinds of tactics,” he said. “In this case, it has brought about a very serious crisis in the Syrian opposition.”

Meanwhile, Shaikh added, the Islamist groups that have emerged as the most effective fighters in the battle for control of Syria also are stepping up to fill the vacuum left by the collapse of governance in areas captured by the rebels, a role the West had been hoping the new coalition would fulfill.

“The irony is that it’s the Islamists and the extremists who are assuming more and more control,” Shaikh said.