The US is "very concerned" about the situation playing out in northwest Syria following the launch of Turkey's 'Operation Olive Branch,' US Secretary of State Rex Tillerson told his Turkish and Russian counterparts in phone conversations on Sunday, according to a US State Department release. The Department has urged its NATO ally Turkey to exercise restraint and ensure that its military operations remain limited in scope and duration, in order to avoid civilian casualties. It comes after German Foreign Minister Sigmar Gabriel said the last thing Syria needed after its fight against Islamic State (IS, formerly ISIS/ISIL) is another military confrontation, underlining that Damascus needs to focus on peace and stability.