Istanbul // A major Kurdish alliance has joined the opposition Syrian National Coalition after more than a year of fraught negotiations, in what may prove a significant breakthrough for the rebels.

The agreement between the Kurdish National Council (KNC) and SNC, Syria’s main political opposition group, comes at a time of increasing violence between Kurdish militia and armed Islamist factions in north-eastern Syria, which has killed scores of people in recent weeks.

Kurds account for 10 per cent of Syria’s population – more than 2 million people - and both the opposition and President Bashar Al Assad have tried to win their support, each believing it could be crucial in tipping the balance of power on the ground in their favour.

Underscoring the complexity of the Syrian conflict, Kurdish factions have held back from wholeheartedly joining the revolt, despite being long-time foes of the Assad regime, and some Kurdish groups continue to cooperate with regime forces.

Sunday’s deal finally brings the Kurdish National Council (KNC), an alliance of influential Kurdish parties, into the SNC.

Under the terms of the agreement, the SNC recognised a change in the name of the country they are struggling to wrest from the control of President Bashar Al Assad’s regime, dropping “Arab” from the Syrian Arab Republic.

That had been a major sticking point during months of talks between the KNC and SNC, with Arab nationalists in the opposition reluctant to change Syria’s formal name, while Kurds insisted it was a holdover from the Baath party era that must be amended because not all Syrians are Arabs.

Another crucial element of the deal was similarly linguistic but also highly sensitive, to change references in official SNC documents regarding “Kurdish ethnicity” to “Kurdish people”.

Rather than being an issue of pedantic terminology, opponents to this change argued it would serve as a precursor to the Kurds pushing for independence, and ultimately, to the division of Syria. The KNC, made up 15 Kurdish political parties, insists the term “Kurd” does not merely refer to an ethnic grouping and has been pushing for Kurdish autonomy.

Kamal Labwani, a prominent Syrian dissident and SNC member, opposed the agreement, calling it “divisive”.

“We needed complete equality before the law for each and every Syrian, regardless of religion, sect or ethnicity, we do not need recognition that certain groups have special rights that others are not allowed,” he said.

“Rather than unifying the opposition, this deal has just made certain that in future there will be a war between the Kurds and the Arabs, and that Syria may get divided up,” he said.

In the end, enough SNC members were mollified by the agreement’s recognition of Kurdish rights “within a framework of a unified Syria, as a people and a land”, according to Anas Al Abdeh, a leading SNC member and architect of the deal.

Disagreements over these points led to a KNC walkout from key opposition talks in Cairo in 2012 and, until Sunday, had remained unresolved.

“It’s a huge step forward. Some people do think this might be used by the Kurds to get independence but all of the [KNC] parties have stated very clearly that they do not aspire for separation,” Mr Al Abdeh said.

Under the agreement, the SNC is also to be expanded to include a new intake of Kurds, in what is a further adjustment of a delicate, and hard fought over, quota system dividing up influence within the SNC’s various factions, including the Muslim Brotherhood, secular dissidents, Free Syrian Army members and grassroots activists.

The expansion may prove another major sticking point. All enlargements of the SNC require approval from two-thirds of all members – rather than 51 per cent of those present in the meeting, which suffices for other procedures..

These technicalities have plagued previous expansion efforts and brought the coalition to the brink of collapse in a series of farcical meetings in Istanbul in May.

Exact levels of support in the SNC for the KNC deal remain uncertain. In Sunday’s ballot approving the basic terms of the agreement, 57 SNC members voted in favour – just enough to pass the motion because not all of the 115 members were present.

But the clauses relating to expansion will have to be voted on again, at another meeting that has not yet been scheduled, and they must win a two-thirds majority – at least 77 votes – to pass.

An added difficulty is that there also seems to be confusion about the number of Kurdish members called for under the deal.

Mr Al Abdeh said the agreement was for 11 Kurdish seats in the SNC and, because three Kurds are already in place, he said that means the expansion will add eight new members, all Kurds.

But the KNC has indicated it does not believe the size of Kurdish representation has yet been set, and an SNC official familiar with discussions said the group was pushing for 11 seats in addition to the three currently held.

Mr Al Abdeh said the deal for eight additional seats was “done and dusted” and was confident it would get voted through with the required two-thirds majority when a vote is held.

Others were less sure.

“Not many people are happy with all of this, especially the removal of ‘Arab’ from the name of the country, that’s a really sensitive issue,” said an opposition political activist familiar with the negotiations.

Bahzad Ibrahim, a leading KNC member, told the AFP news agency that the agreement represented progress “towards guaranteeing that Syria will be more inclusive and that the opposition can better represent the Kurds”.

In Kurdish circles – where a struggle is under way between different parties and ideologies – the deal is also controversial, drawing criticism from People’s Protection Units (YPG), an armed group affiliated with the Democratic Union Party (PYD).

Both the YPG and PYD have wide popular support among Syrian Kurds and remain outside the KNC.

They have also been fighting against rebel factions, primarily militant Islamist groups such as Al Nusra, but also Free Syrian Army units ostensibly under the command of the SNC – of which the KNC is now a part.

That means Kurds are now backing opposition groups ranged against one another on the battlefield..

“We call on the Kurdish National Council (KNC), which joined the Syrian Coalition (SNC), which supports these attacks against Kurdish areas, to openly declare if it too supports the war against the Kurdish people or not,” the YPG said.

Political divisions among Syria’s Kurds remain acute, with KNC parties accusing YPG-affiliated police forces of arresting members and detaining pro-democracy activists.

The political agreement is unlikely to halt the violence in north-eastern Syria, where repeated efforts to broker a ceasefire have failed.

The PYD and YPG have come in for heavy criticism from the Syrian opposition and some Kurds for maintaining links with the Assad regime and allowing it to launch attacks on rebels from Kurdish territory. The YPG counters this by saying they are protecting Syria’s Kurds against radical Islamists, including Al Qaeda.

psands@thenational.ae