BEIRUT (AP) -- Syria's Western-backed opposition plunged into disarray on Sunday as its president resigned and its military leader refused to recognize a prime minister recently elected to lead an interim rebel government.
The chaos inside the opposition Syrian National Coalition threatened to undermine its bid to unite the forces battling President Bashar Assad and better organize the fight to oust his regime. It also could hamper support from the U.S. and other powers, who have hoped the Coalition would emerge as the most credible body to channel aid to anti-Assad groups inside Syria and undermine the Islamic extremists who dominate the fight on key fronts of the nation's civil war.
As the opposition's political leadership stumbled, rebel fighters inside Syria pressed ahead Sunday with their offensive in a restive southern province that borders Jordan. Also, Israel's military said its forces in the occupied Golan Heights responded to fire across the border by shooting at a target inside Syria.
In his surprise resignation Sunday, Coalition president Mouaz al-Khatib expressed frustration with the both the international community and the opposition body itself. Al-Khatib, a respected preacher who has led the Coalition since its creation late last year, said in a statement posted on his Facebook page that he was making good on a vow to quit if certain undefined "red lines" were crossed.
"I am keeping my promise today and announcing my resignation from the National Coalition so that I can work with freedom that is not available inside the official institutions," he said.
He also blamed world powers for providing what he deemed insufficient support for the rebel cause, and complained that many "international and regional parties" have insisted on pushing the opposition toward dialogue with the regime. Most opposition leaders and activists say Assad's regime has killed too many people to be part of a solution to the conflict.
"All that has happened to the Syrian people -- from destruction of infrastructure to the arrest of tens of thousands to the displacement of hundreds of thousands to other tragedies -- is not enough for an international decision to allow the Syrian people to defend themselves," the statement said.
Despite electing a new, U.S.-educated prime minister to head a planned interim government last week, the Coalition has failed to establish itself as the top opposition authority on the ground in Syria, where hundreds of independent rebel brigades are fighting a civil war against Assad's forces.
The Coalition's media office distributed al-Khatib's statement, but did not comment on how his replacement will be chosen.
Al-Khatib's spokesman, Ali Mohammed Ali, confirmed the authenticity of the statement in a phone call with The Associated Press. He declined to discuss any issues inside the Coalition that could have influenced al-Khatib's decision.
Burhan Ghalioun, the former head of the Syrian National Council, which preceded the Coalition, said that he and other Coalition members were surprised by the resignation.
Speaking on Al Arabiya TV, Ghalioun also said he assumed the decision was a protest against world powers that have not provided the opposition with the aid it needs, as well as against unnamed countries that have interfered in the Coalition's operations and other Coalition members who have impeded al-Khatib's work.
"I lived this, so I know what it means," Ghalioun said, speaking of his own resignation as head of the SNC last year.
Secretary of State John Kerry said he was sorry to learn of al-Khatib's resignation, but that it won't affect U.S. cooperation with the Coalition on aid.
He called such transitions natural, adding that it shows "an opposition that is bigger than one person, and that opposition will continue."
The second blow Sunday to the opposition leadership was delivered by the head of the Coalition's own military branch, Gen. Salim Idris, who refused to recognize the body's new prime minister, saying he did not represent many anti-Assad groups.
Last week, the Coalition elected a little-known U.S.-educated IT expert named Ghassan Hitto to head a rebel interim government.
But in a video statement posted online and distributed by his aides Sunday, Idris said his group would only support a prime minister with broad backing.
"For the purpose of giving power to a prime minister to unite the revolutionary forces and lead the Syrian revolution toward certain victory, we unequivocally declare that the Free Syrian Army in all of its formations and revolutionary powers conditions its support and cooperation on the achievement of a political agreement on the name of a prime minister," he said.