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 rebel Free Syrian Army's decline comes ahead of January peace talks that ascendant Islamist rebel groups have rejected, raising concerns that even if the opposition struck a deal with the regime it would be unable to deliver.
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 key regime all Iran and Saudi Arabia, a backer of 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 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 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.
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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.
Media appeal against kidnappings
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.
The Syrian Observatory for Human Rights said Thursday that rebels had killed at least 15 mainly Alawite civilians at Adra in Damascus province.
Residents of the multi-confessional town told AFP 10 of them were killed for collaborating with the regime.
Meanwhile, 13 major news organisations, including AFP, have called on the leadership of Syria's rebels to ensure journalists working in opposition areas can do so free from the threat of kidnap.
"We ask the leadership to assist in identifying those groups currently holding journalists and take the steps necessary to bring about their release," they said in a letter addressed mainly to the FSA and the Islamic Front.
News organisations estimate that more than 30 journalists are being held in Syria.
In fighting on the ground, Assad's forces have 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.