By Tom Perry
BEIRUT (Reuters) - Western-backed fighters in southwestern Syria, the one part of the country where they are still strong, have spoken out against al Qaeda, a move could lead to fighting among of President Bashar al-Assad.
The most powerful opponents of Assad in Syria's civil war are Sunni Muslim jihadists from two groups: the Islamic State, also known as ISIL or ISIS, and al Qaeda's Syria branch, the Nusra Front. Western and Arab countries which oppose both Assad and the jihadists aim to support what Washington calls "moderate" rebels.
Although such Western-backed fighters control comparatively little territory, an alliance known as the Southern Front has an important foothold near the borders with Jordan and Israel. It has seized a border crossing and a government-held town in recent weeks after weathering a government offensive.
Nusra, which has crushed pro-Western rebels in the north, is also active in the south and has sometimes joined Southern Front groups in battle against government forces, making their relationship ambiguous.
But this week, Southern Front groups issued a strong statement condemning Nusra's ideology, rejecting any cooperation with it, and declaring themselves the "sole military force representing the Syrian revolution" in the south.
"It is not a call for war but they will understand it that way, and if they want to fight they will be the losers," said Abu Ghiath al-Shami, spokesman for the Alwiyat Seif al-Sham, one of the Southern Front groups.
With aid funneled via U.S. ally Jordan, the Southern Front groups are stronger than the jihadists in the south, according to several assessments including one provided by a U.S. intelligence official.
"We must announce our clear position: neither the Nusra Front or anything else with this ideology represents us," said Bashar al-Zoubi, head of a rebel group called the Yarmouk Army.
"We can't go from the rule of Assad to Zawahiri and Nusra," said Zoubi referring to the al Qaeda leader Ayman al-Zawahiri.
Aboul Majd al-Zoubi, head of a Southern Front-linked Syrian Media Organisation, said the aim is to isolate Nusra. "The door is open for Nusra Front fighters to defect and to join the factions of the Southern Front," he said.
The statement appears to have been prompted by incidents including an attempt by Nusra to arrest a Southern Front commander, and tension between the sides at the Nasib crossing with Jordan. The crossing was seized from the government on April 1, with both the Southern Front and Nusra claiming to have played the decisive role in taking it.
Islamic State currently has little presence in the south but may be eyeing expansion there. Its fighters staged an assault on an air base in Sweida province in recent days, part of a pattern of attacks beyond its eastern strongholds, which was repelled by the Syrian army.
Bashar al Zoubi said that attack was an attempt by Islamic State to announce its arrival in the area, and that more international support for the Southern Front was needed to help stave off the jihadist threat.