istanbul turkey say tuesday could expand military mission syria two provinces potentially bring force confrontation u.s.-backed kurdish fighters ankara consider enemies turkish troop operate observation mission rebel-held territory syria northwestern idlib province deal damascus ally russia iran help reduce fight insurgents government force consider observation mission turkish arm force idlib de-escalation zone continue successfully mission perform near western aleppo afrin would provide real environment peace safety turkey national security council say statement ankara long back rebel fight overthrow president bashar al-assad tone demand assad leave power say main concern syria combat islamist militants kurdish fighters consider ally kurdistan workers party pkk fight decades-long insurgency southeastern turkey early month turkish president tayyip erdogan say turkey need clear afrin region northwest syria kurdish ypg militia fighters military operation idlib province largely complete kurdish ypg main element u.s.-backed force washington assist train weapons air support help grind advisers battle islamic state washington support ypg bone contention unite state turkey ally nato turkey suggest plan extend military mission syria afrin aleppo