U.S. military officials said on August 29 that fighting in northern Syria between Turkey's army and U.S.-backed Syrian Kurds is "unacceptable."
A Pentagon statement said the clashes that have been intensifying in northern Syria "only provide room for Islamic State (IS) militants to find sanctuary and plan attacks against Turkey, the United States, and others."
The statement also reiterated the U.S. view that all Syrian Kurdish YPG militia fighters in northern Syria should cross to the east side of the Euphrates, saying the Pentagon "understands this has largely occurred."
The Pentagon statement was issued after correspondents reported on August 29 that the Turkish Army and a Turkey-backed Syrian rebel group called Sultan Murad were battling Syrian Kurdish YPG militia fighters near the Kurdish-held city of Manbij on the west side of the Euphrates River.
A commander of the Sultan Murad group said on August 28 that his forces intend to capture Manbij from the Kurdish fighters.
Turkish Foreign Minister Mevlut Cavusoglu said on August 29 that the Kurdish Syrian YPG fighters who have been battling IS militants in northern Syria must withdraw east of the Euphrates river "immediately" or face more military strikes from the Turkish forces that crossed the border on August 23.
Ankara says the Syrian Kurdish fighters are terrorists. Turkey wants to stop the YPG from controlling territory along Turkey’s border with Syria.
Meanwhile, Syrian opposition groups reported on August 29 that the Turkish-backed Syrian rebels have captured more towns and villages in northern Syria and were taking up battle positions around the city of Manbij -- which the YPG captured two weeks ago from IS militants after a 10-week operation that was supported by U.S. air strikes.
The Pentagon, which sees the YPG militia as an important strategic part of the U.S.-led anti-IS coalition, says U.S. forces were not involved any clashes between the YPG and troops taking part in the Turkish ground offensive.
The Pentagon says its support for Turkey’s military incursion in northern Syria is only for operations targeting Islamic State militants.
YPG spokesman Redur Xelil on August 29 denied reports of Kurdish troop movements into Manbij, saying "there are absolutely no YPG military reinforcements being sent towards Manbij."
On August 24, Xelil said Kurdish forces would not retreat to the east of the Euphrates -- maintaining that YPG forces to the west of the Euphrates River were in their own country.