Beirut: Rebel groups from northern and eastern Syria on Wednesday demanded aid from the country`s exiled opposition to allow them to fight against the jihadist Islamic State (IS) group.
"We, the leaders of the brigades and battalions... give the National Coalition, the (opposition) interim government, the (rebel) Supreme Military Council and all the leading bodies of the Syrian revolution a week to send reinforcements and complete aid," the statement said.
"Should our call not be heard, we will lay down our weapons and pull out our fighters," it added.
The statement comes three days after IS declared the establishment of a "caliphate" straddling Syria and Iraq, referring to an Islamic system of rule that was abolished nearly 100 years ago.
"Our popular revolution (against Syrian President Bashar al-Assad)... is today under threat because of the (Islamic State), especially after it announced a caliphate," said the statement.
IS first appeared in Syria`s war in late spring 2013. It has since taken control of Raqa in northern Syria, much of Deir Ezzor in the east, and parts of Aleppo province.
The factions that signed the statement are local rebel groups based in the areas where fighting against IS has been most intense, and which are now under IS control.
Rebel groups from those areas have frequently complained of poor funding, despite their opposition to IS, formerly known as the Islamic State of Iraq and the Levant.
Some Syrian rebels seeking Assad`s ouster initially welcomed the war-hardened IS fighters among their ranks.
But their systematic abuses and quest for hegemony in opposition-held areas eventually turned the rebels against them and their project.
IS has kidnapped thousands of Syrians, many of them political activists and rebels, and carries out summary executions in areas under its control.
The group has been bolstered in recent weeks by an offensive it spearheaded in neighbouring Iraq, capturing large swathes of territory as well as heavy weapons seized from fleeing Iraqi troops.
Syria`s war began as a popular revolt demanding Assad`s ouster, but morphed into a war after his regime unleashed a brutal crackdown against dissent.
Many months into the fighting, jihadists started to pour into Syria, and in January 2014, the country`s rebels including Islamists launched a major offensive against IS.