“Such unilateral military actions in northeastern Syria are a matter of serious concern, especially when the US military can be nearby ... We would consider any such action unacceptable and thus again call on Turkey to work with us on a common approach,” she said.

A State Department spokeswoman added that the US authorities "continue intensive discussions with Turkey about the security zone."

Earlier, Turkish President Recep Tayyip Erdogan said that Ankara intends to soon carry out an operation against militants on Syrian territory on the east bank of the Euphrates.

July 30 reported that Turkey plans to create a security zone along its borders in northern Syria.