Syrian rebels say advance against ISIS could take months

Syrian rebels, who this week seized a strategic town from ISIS, aim to move westward in the next phase of their Turkey-backed operation, an advance that could take weeks or months to complete, a rebel commander said.

Col.Ahmad Osman, head of the Sultan Murad group, also told Reuters the rebels did not wish to fight Kurdish forces that have advanced in northern Syria as part of a separate campaign against the Islamic State in Iraq and Syria (ISIS), but would do so if necessary.

Sultan Murad is one of the main Syrian rebel groups taking part in the operation that on Wednesday drove ISIS from the border town of Jarablus with help from Turkish special forces, warplanes and tanks.

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The operation aims to expel ISIS from its last foothold at the Syrian-Turkish border, but also to prevent any further gains by the Kurdish YPG militia whose growing influence in Syria has alarmed Turkey as it battles its own Kurdish insurgency.

Osman, speaking to Reuters fromJarablus, said the priority was now to advance some 70 kilometreswestward toMarea, a town where rebels have long had a frontline with ISIS.

"We want to cleanse this area before moving south,"Osmansaid. Failing to do so would leave the rebels at risk of ISIScounter attack, he said. "The priority is from Jarablus in the direction of al-Rai, reaching Marea."

Al-Rai is a village between Jarablus and Marea captured by rebels this month. Osman said there were dozens of villages between Jarablus and Marea that must be recaptured from ISIS.

"Liberating these villages betweenJarablusandMarearequires weeks and perhaps months, according to the nature of the battles," he said.

Several rebel groups are taking part in the operation, fighting under the banner of the Free Syrian Army.They have received varying degrees of help from Syrian PresidentBasharal-Assad'sforeign enemies, including military aid and training.

Osman, 49, said both Turkey and the U.S.-led coalition against ISIS, of which Ankara is a part, were keen to provide air support for the operation.

The rebel factions have also advanced southward fromJarablustoward the city ofManbij, which was captured earlier this month from ISISby the U.S.-backed Syrian Democratic Forces (SDF) alliance including Kurdish fighters.

The SDF crossed the Euphrates river in order to attackManbij. Turkey has demanded the Kurdish YPG fighters now go back across the river.The rebels fighting with Turkish support are hostile to the YPG, with the sides clashing repeatedly since last year.

Turkey,quoting U.S. Secretary of State JohnKerry, said earlier that theSyrian Kurdish forces hadstarted withdrawing east of the Euphrates River, heeding warnings from both Turkey and the U.S.

Earlier Thursday, Reuters reported the Turkishmilitary shelled a group of Syrian Kurdish fighters south of the town ofJarablus.

"We are currently planning not to confront them, but if we have to confront them, we will,"Osmansaid.

Osman, who defected from the Syrian military to join the uprising in 2012, said that for some operations, the number of rebel fighters may need to be increased from its current level of between 1,200 and 1,500.

"We are ready to supply greater numbers, depending on the nature of the battle," he said.

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