BEIRUT: The leader of al-Qaeda's Syrian wing tried unsuccessfully at a recent meeting to convince rival Islamist factions to merge into one unit, several insurgency sources have told Reuters.

Abu Mohamad al-Golani, head of the Nusra Front, even suggested he was willing to change the name of his group if the others, including the powerful Ahrar al-Sham organisation, agreed to the deal, the sources said.

But he made clear that Nusra would not cut its ties with al-Qaeda, and its allegiance would remain to Ayman al-Zawahri, who took over as leader after US Navy SEALS killed Osama bin Laden in 2011.

Much was riding on the outcome of the meeting, which the sources said took place about 10 days ago.

Nusra and Ahrar al-Sham are the most powerful groups in northern Syria: when they briefly teamed up with other Islamists last year in an alliance called the Fatah Army, the rebels scored one of their biggest victories by seizing the city of Idlib.

Some rebels believed a merger would create a stronger rival to Islamic State and might attract much-needed military support and recognition from regional and international powers.

But the leaders left without an agreement, and the sources said the atmosphere was tense, with Nusra blaming Ahrar al-Sham for the failure.

A few days later, members of the two groups clashed in the towns of Salqin and Harem in Idlib province, near the border with Turkey. Several fighters were killed on both sides, but other insurgent groups brokered a quick ceasefire.

Jihadi sources, including some from Ahrar al-Sham, say it is only a matter of time before another battle between the two erupts. They say the rift between them is getting deeper, although mediation continues. One restraining factor has been an imminent assault by the Syrian rebel army and its allied forces in northwestern Syria.

"The situation is charged, the failure of initiatives could cause an explosion," said a jihadi in Idlib who is close to the two groups. "What happened just avoided all-out conflict, all-out battle. But it will be hard to tell what will happen in the future."

Outright war between Nusra and Ahrar al-Sham would still further complicate the five-year Syrian conflict, in which rebel groups are mushrooming under different slogans and sometimes fighting each other.

A delegation from Syria's main opposition group, the Saudi-backed Higher Negotiation Committee (HNC), arrived in Geneva on Saturday to join United Nations-mediated peace talks, demanding President Bashar al-Assad's government be made to comply with a UN resolution on humanitarian aid and human rights.

Nusra and Islamic State - designated as terrorists by the UN have been excluded from the Geneva talks, the first attempt in two years to end a war that has killed a quarter of a million people. Ahrar al-Sham, which presents itself as a Syrian nationalist force in contrast to al-Qaeda's global jihadist ideology, recently joined the HNC but Russia opposes its participation in the talks.