Pentagon calls for end to fighting
Turkey warned predominantly Kurdish Syrian fighters on Monday to "immediately" withdraw east of the Euphrates River or face more strikes by Turkish forces that crossed the border last week in Ankara's major incursion into Syria.
Pentagon, meanwhile, called on NATO ally Turkey and the predominantly Kurdish US-backed fighters aligned against the Islamic State group to stop fighting each other in northern Syria. In a written statement, Pentagon press secretary Peter Cook called the clashes south of the Euphrates River town of Jarablus in Syria "unacceptable" and a source of "deep concern".
However, Kurdish-backed forces later said they will only pull back south from their current positions, in order not to put the lives of civilians in danger following attacks by Turkey-backed Syrian rebels.
The Kurdish announcement came hours after the warning by Turkey's Foreign Minister Mevlut Cavusoglu - and is unlikely to satisfy Ankara.
The sharp rhetoric - and the continued fighting - reflects the quagmire in northern Syria after Turkish tanks rolled across the border last week to help Syrian rebels seize the town of Jarablus from the Islamic State group, a move that was also aimed at deterring further advances by the Kurdish-led forces.
The fighting now pits Turkey, a NATO ally, against the Syrian Kurdish force - a US-backed proxy that is the most effective ground force battling IS militants in Syria's five-year-old civil war. It leaves Washington in the tough spot of having to choose between two allies and is likely to divert resources from the fight against IS.
Turkey's top diplomat spoke on Monday as Syrian opposition groups reported that Turkish-backed Syrian rebels have captured more towns and villages in northern Syria as part of the operation named 'Euphrates Shield', now in its sixth day.
Cook said the US doesn't support reported Turkish air strikes and artillery shelling of US-backed Syrian Kurdish fighters or Kurdish attacks on Turkish troops in areas where IS fighters no longer are operating.
The United States and Turkey have called on the Syrian Kurdish People's Protection Units, or YPG, to pull back to the east side of the Euphrates, in accordance with US assurances given to the Turks, and Cook said this pullback has "largely occurred".