BEIRUT: Syria's Western-backed rebels were in disarray Thursday after Washington and London suspended non-lethal aid following the loss of a key border crossing and arms depots to a powerful Islamist alliance.
The decline of the rebel Free Syrian Army comes ahead of January peace talks that the ascendant Islamist rebel groups have rejected, raising concerns that even if the opposition reached a deal with the regime it would be unable to implement it.
The talks, dubbed Geneva 2 after a previous meeting in 2012, will be held in the Swiss city of Montreux with an estimated 30 countries invited, including Iran, a key regime ally, and Saudi Arabia, which has backed the rebels, diplomats told AFP.
The January 22 conference is aimed at ending the nearly three-year civil war, which has claimed an estimated 126,000 lives and displaced millions, including thousands now in tent camps blanketed with snow.
But no armed rebel groups have said they will join the talks, and Islamist groups have warned that anyone attending will be considered a "traitor".
The Islamic Front, a powerful alliance formed last month, is now the largest rebel force, with tens of thousands of fighters.
The alliance does not include the Islamic State of Iraq and the Levant (ISIL) or Al-Nusra Front, two hardline Al-Qaeda affiliates.
But last week it withdrew from the FSA's Supreme Military Council headed by General Selim Idriss, and over the past week it has seized the Bab al-Hawa crossing on the Turkish border and arms warehouses from his forces.
The seizure prompted the United States and Britain to suspend non-lethal aid to the FSA, dealing a major blow to a group that increasingly appears caught between advancing regime forces and the increasingly unified Islamists.
"While there is definitely a case of Syria's Islamists getting stronger, it is also clear that the Supreme Military Council (SMC) is growing weaker, that it has lost power," said Aron Lund, a Sweden-based expert on Syria's insurgency.
"The SMC has lost the border crossing at Bab al-Hawa -- so Idriss may not be able to go into Syria -- as well as the warehouses. Without the warehouses, what do they have?"
The Wall Street Journal reported that Idriss fled to Turkey and then Qatar after the border seizure, but a spokesman for the opposition National Coalition denied this, saying he was meeting with FSA and Islamic Front rebels in southern Turkey.
The SMC also denied the report, saying Idriss "is present at this time, performing all of his functions and meeting with fellow senior military leaders and frontline commanders".
The FSA emerged two years ago as Syria's initially peaceful uprising escalated into an armed revolt after President Bashar al-Assad launched a brutal crackdown.
As defecting soldiers swelled its ranks, the FSA evolved into an umbrella organisation for channelling arms and funding to fighters, and under Idriss's leadership came to be seen in the West as the best hope of toppling Assad.
But the group has lost ground as Western nations have refused to supply the heavy weapons it says it needs, fearing they would fall into the hands of jihadists and other Islamists, which have their own sources of arms and funding.
"From the beginning, the Islamist battalions were the only ones receiving assistance," even when they operated under the FSA, said Selim Hijazi, head of the Damascus-based Liwa al-Sham, part of the FSA.
Ever since the Islamic Front was set up, "the FSA has stopped receiving aid altogether", he told AFP via the Internet.
The latest decision to suspend non-lethal aid -- including flak jackets, tents, binoculars, radios and medical equipment -- is mainly symbolic.
"At this point, the FSA brigades have their own back-up supply of lethal and non-lethal assistance so we don't see it as a critical problem," opposition spokesman Khaled Saleh told AFP.
Assad's forces have meanwhile been advancing, including in the strategic Qalamoun region along the Lebanon border, and the Damascus delegation appears set to go to Montreux in a position of strength.
Among the rebels, meanwhile, there are "revolutions against revolutions, coloured by military coups", said Abu Leila, a rebel based in the northern Idlib province.