Turkey worries about expanding cooperation between US-led coalition and Kurdish YPG forces.
The Syrian border town of Jarablous could soon become a battleground and that battle could change the front-lines and the balance of power in territories outside the control of the government in northern Syria.
Jarablous is controlled by the Islamic State of Iraq and the Levant (ISIL). Its flag is hoisted just a few metres from the Turkish flag at the border crossing.
A fence is what demarcates what has been a quiet frontier for years.
Just 100 metres from where we were standing, we could see a bulldozer digging trenches around the town's perimeter. A few days ago, ISIL fighters were filmed planting explosives.
The group is preparing for war.
This is the last Syrian-Turkish border crossing ISIL controls. It cannot afford to lose it. Last month, it was pushed from Tal Abyad and the main Syrian Kurdish fighting force, the YPG, claimed control of 400 of the 900km Syrian-Turkish border from Iraq to the town of Kobane in the west.