Amman // Moderate opposition factions and Islamist rebels from Jabhat Al Nusra were on the brink of going to war with each other on Sunday night in what would be a dramatic spread of rebel-on-rebel violence to Syria’s southern front.

Mediation efforts, under way since last Saturday’s capture of Ahmed Nehmeh, a commander in the western and Gulf-backed Free Syrian Army (FSA), were continuing in northern Jordan in a last-ditch attempt to avert an outbreak of open hostilities among rebels.

A deadline set by the FSA for Col Nehmeh to be handed over to an independent court to face allegations of treason was due to expire at midnight. Al Nusra has insisted he face trial by a court in which they and two other allied Islamist factions, Harakat Al Muthanna and Ahrar Al Sham, sit in judgment.

Judges from rebel-controlled courts in Deraa province and field commanders from different fighting units met in Irbid, near the Jordan-Syria border, at the end of a week of frantic, fruitless talks over Col Nehmeh’s fate.

In stark contrast to the fratricidal chaos that has seen rebels in northern Syria fighting one another since mid-2012, they have remained relatively united in the battle against president Bashar Al Assad in the southern zone between Damascus and the border with Jordan, centred on the city of Deraa, where the revolt began in March 2011.

Until now, the FSA and Al Nusra, together with other non-aligned Islamist factions such as Harakat Al Muthanna, have, to a greater or lesser extent, cooperated in operations and shared weapons and intelligence.

That unity has been stretched to breaking point, according to senior rebel sources, after Al Nusra seized Col Nehmeh and, on Thursday, captured another FSA commander, Zuhair Dabo, following clashes in the town of Nawa.

In that incident, an Al Nusra leader known as Emir Sharei was killed, together with at least one FSA fighter. Conditions across the southern front have been tense ever since.

“The reality we are now facing in the south is to see fighting between rebels like we have seen in the north, we’re worried that the Aleppo scenario is going to happen here now,” said a senior FSA commander.

Another leading FSA officer from Deraa said moderate factions were ready to fight Al Nusra if necessary over Col Nehmeh, in order to uphold the principle that the Al Qaeda-affiliated group cannot simply detain commanders of other rebel outfits at will. “We don’t want to go to war with Nusra – we should all be fighting Assad. But we are prepared to take action if we must,” the FSA officer said. “Nusra is testing us and want to see how we will react to their arrest of Nehmeh.

“They are playing a very dangerous game. We will negotiate because we do not want unnecessary bloodshed but if they do not hand him over, there will be serious repercussions.”

Col Nehmeh is commander of the Deraa Military Council (DMC), a link in the FSA’s chain of command between units on the ground and their headquarters in Turkey. He is also a key liaison between western and Gulf backers of the rebels and fighting units.

Following Col Nehmeh’s capture on Saturday, a film showing him battered and bruised after a violent interrogation was posted on YouTube. It showed him confessing to helping foreign intelligence agencies undermine the war effort against the regime in a strategically important battle at Khirbet Ghazaleh a year ago.

After two months of heavy combat, rebels had all but won control of the town – a major regime weapons supply route – until a series of disastrous command decisions handed victory to Assad’s troops.

Al Nusra wants Col Nehmeh to stand trial over the debacle, saying he helped orchestrate the defeat.

FSA units have also criticised Col Nehmeh over Khirbet Ghazaleh and have agreed he should face charges against him. But they want a neutral court, containing representatives from all factions, including Al Nusra, to examine the evidence and decide on his guilt or innocence.

While Col Nehmeh is unpopular among most FSA groups, he retains support within some factions and, more significantly, his office symbolises the moderate wing of the armed rebellion, which until now has remained the major power in the south.

His capture is a potent signal of Al Nusra’s challenge to that primacy.

Al Nusra has been growing in strength in the south, according to rebels and activists in the area, who say that over the past two months the Al Qaeda group has gained in power and confidence, and now feels able to threaten FSA units.

“Nusra is flexing its muscles, they want to be accepted as equals on the battlefield in the south. They are saying, ‘We are not the little brother any more’,” said an FSA commander.

psands@thenational.ae