Jarablus
© Stringer/ReutersAirstrike smoke rises in Jarablus, a border town near Karkamis, Turkey.
The US has agreed to help Turkey capture the border city of Jarablus in Syria to appease Ankara, which was concerned it would fall to Kurdish fighters. US warplanes are carrying out airstrikes in support of the operation, a Pentagon official said. On Wednesday, Turkey sent special forces and tanks to seize the border city of Jarablus in northwestern Syria from Islamic State (IS, formerly ISIS/ISIL), which has been in control of it since 2013.

Turkish artillery has been pounding targets in Syria for two days and Turkish warplanes are providing aerial support for the troops on the ground in their first foray into Syrian airspace since November of last year, when a Turkish fighter jet shot down a Russian bomber near the Syrian-Turkish border.

US drones based at Incirlik Air Base in southern Turkey are assisting the operation by carrying out surveillance missions over the combat zone, the Wall Street Journal reported, citing US officials. American military advisers on the Turkish side of the border are reportedly helping to plan the offensive. "We are syncing up with the Turks," a senior US official told the WSJ. "We have full visibility on what they are doing." American A-10 'Warthog' ground attack aircraft and F-16 figher jets are carrying out airstrikes in support of the Turkish ground operation, a Pentagon official told Reuters.

The coordinated attack is meant to capture Jarablus and hand it over to Turkish-backed Syrian rebels before Syrian Kurdish forces can take it, the report said. The Kurds recently took the city Manbij south of Jarablus and have been pushing north.

In principle, the US is allied with the Kurdish militia, the YPG, but in this case it has sided with their Turkish enemies. Ankara sees the YPG as allies of the Kurdish insurgency in Turkey, which has been waging a guerrilla war against the Turkish government for four decades. Though Jarablus is a Kurdish city, Ankara is concerned that should the strategic settlement fall back under Kurdish control, it would compromise Turkish national security.

"We've put a lid on the Kurds moving north, or at least doing so if they want any support from us, which I think is a fairly significant piece of leverage," the US official told the WSJ. "So for the moment I think we've put a lid on the biggest concern that the Turks have, which I think gives us some breathing space to make sure this operation in Jarabulus [sic] is done the right way and that we and the Turks do it together."

Washington does not want Turkish and Kurdish forces to engage in direct combat, a point Vice President Joe Biden tried to make during his visit to Turkey. "No (Kurdish) corridor. Period. No separate entity on the Turkish border. A united Syria," the vice president said at an earlier news conference with Turkish Prime Minister Binali Yildirim.

Biden arrived in Turkey hours after the operation began. The pre-planned trip is seen as an attempt to smooth relations between the two countries.

Turkish and Kurdish forces have targeted each other with artillery fire in the past and Turkey has extensively used its warplanes to conduct airstrikes on Kurdish targets in Syria and Iraq over the past few years.

Relations between the US and Turkey soured recently after Ankara perceived a lack of support from the US in the wake of a failed military coup last month. Senior Turkish officials said the US had sided with self-exiled Turkish cleric Fethullah Gulen, who they want extradited for trial. Gulen denies any involvement in the coup attempt, and the US has refused to hand him over, so far.