BEIRUT - US-backed Syrian fighters in the Manbij area of northern Syria have deployed to frontlines to confront a threatened Turkish assault and are in contact with the US-led coalition over protecting the city, their spokesman said on Wednesday.Turkey has launched an air and ground operation in Afrin in northwest Syria targeting the US-backed Kurdish YPG militia - seen by Ankara as a threat to its security - and has threatened to extend its operation some 100 km (60 miles) eastwards to Manbij.Unlike Afrin, Manbij is an area where the United States has military personnel stationed, raising the risk of possible confrontation between the NATO allies amid Turkish fury over US support for the YPG militia.Manbij is bordered to the west by a stretch of territory controlled by Turkey-backed Free Syrian Army groups."Of course we in the Manbij Military Council have taken the necessary measures and deployed our forces to the front lines," said Sharfan Darwish of the Manbij Military Council."We are in full readiness to respond to any attack (by Turkey and its allies).""Of course our coordination with the international coalition continues with regards to the protection of Manbij," he added.Darwish said the US-led coalition had stepped up patrols in the Manbij area in apparent response to the Turkish threats, though a coalition spokesman said there was no indication that this was the case."I don't have any indications to say there has been any frequency changes in the amount and how often we do patrols," coalition spokesman Colonel Ryan Dillon said. "We have been conducting patrols in that area for more than a year now, and overtly. Those have continued and they continue today."He added: "Clearly we are very alert to what is happening, specifically in the area of Manbij because that is where our ... coalition forces are.""The coalition forces that are in that area, have an inherent right to defend themselves and will do so if necessary," he said.