Meanwhile, Turkish forces detained 18 people, suspected of being part of Syria's regime forces, in the northern town of Ras al Ayn, Ankara said.
Damascus has had a tactical relationship with the PKK since the 1970s, when the terror group was in its infancy. Now the old ties are being renewed in light of Turkey's military operation in northern Syria.
US Defense Department says American troops in northern Syria were shifted "out of the path of potential Turkish incursion." Ankara says its campaign against terrorists is meant to establish a peace corridor to resettle millions of displaced Syrians.
Turkey will be aided the recently formed Syrian National Army, which is made up of various rebel and opposition groups, for its operation into northern Syria to clear the YPG from the country's border.
US President Trump defends decision to withdraw US troops from northern Syria, where Turkey plans a military campaign, saying it was too costly to keep supporting SDF/ YPG militants.
The announcement comes a day after Ankara sent military reinforcements to its southern border. Turkish President Erdogan says Turkey is ready to target terror groups in northern Syria, with or without support from the United States.
Turkey's President Recep Tayyip Erdogan on Saturday gave the most direct indication of a military offensive since Ankara and Washington decided to establish a "safe zone" in the region.
"We made our preparations. When necessary, we can take matters into our own hands," Hulusi Akar says.
Turkey's President Erdogan says Ankara plans to settle 2 million Syrian refugees in "safe zone", which would run from Euphrates river in Syria to Iraqi border. But Western allies are yet to respond to Turkish calls for funds.
Close to Euphrates river in Iraq's restive Anbar province, Al Qaim crossing faces Al BuKamal in Syria's vast eastern region of Deir Ezzor and was recaptured from Daesh in November 2017.
Two Turkish and two American helicopters took off from Sanliurfa, southeastern Turkey, where the two countries’ armed forces have a joint operations centre.
Turkish President Recep Tayyip Erdogan is set to attend the 74th session of the UN General Assembly in the US.
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