US President Barack Obama will meet his Turkish counterpart Recep Tayyip Erdogan on Sunday in China on the sidelines of the Group of 20 summit, with Syria high on the agenda, top aide Ben Rhodes announced Monday.

"They will be discussing the counter-ISIL campaign and the fact that we need to stay united," Ben Rhodes, the deputy US national security advisor, told reporters.

Turkey has launched military operations inside Syria against both Islamic State (IS) jihadists and the US-backed Syrian Kurdish People's Protection Units (YPG), creating a dilemma for Washington.

Clashes between the Turkish forces and the YPG over the weekend drew a sharp rebuke from the Pentagon, which called them "unacceptable."

A US defense official said the US-backed Kurdish forces had pulled back to east of the Euphrates river over the past day or so, as demanded by Ankara.

Turkey, a key NATO ally, regards the YPG as "terrorists," while the United States considers the militia an effective force against IS in Syria.

Obama's meeting with Erdogan would be their first since a failed coup attempt in Turkey on July 15.

Tensions between the two allies have risen sharply since then, with Turkey demanding that the United States extradite Fethullah Gulen, an exiled former imam who Ankara claims was behind the coup attempt.