“Any uncoordinated military operations by Turkey will undermine that shared interest," Ortagus said on Monday.
On Sunday, Turkish President Recep Tayyip Erdogan said that Ankara would launch a new military operation in Syria east of the Euphrates River. Erdogan added that Turkey had informed the United States and Russia of its plans regarding the military operation.
Orgatus said that the US government has seen the reports on Turkey’s possible military operation in Syria.
“We continue intensive discussions with Turkey on a safe zone to address their legitimate security concerns along the Turkey-Syria border,” Ortagus said.
The State Department spokesperson expressed confidence that such discussion is the way to secure the Turkey-Syria border area and urged Ankara to cooperate with Washington to solve the issue.
However, Ortagus warned that the United States would find a unilateral military operation by Turkey in Syria unacceptable.
“Such action into northeast Syria, particularly as US personnel may be present or in the vicinity, while our and local Syrian partner’s operations against the Islamic State* holdouts are continuing, is of grave concern,” Ortagus said.
Earlier on Monday, a source in the Turkish military said that Ankara may launch a military operation to the east of the Euphrates river after the Islamic Eid al-Adha holiday on August 11.
The territory east of the Euphrates is currently controlled by the US-backed Self-Defence Force, which mainly includes Kurdish-led militia.
Turkey has repeatedly launched operations against Kurdish forces in southwest and northern areas of Syria as well as in the northern parts of Iraq.
In 2018, a Turkey-led Operation dubbed Olive Branch started in the predominantly-Kurdish district of Afrin in northern Syria. In March, Turkey announced it would undertake an operation in northern Iraq against the Kurdistan Workers' Party (PKK), designated by Ankara as a terrorist organization.
*Daesh (ISIL/ISIS/Islamic State/IS), a terrorist group banned in Russia and a wide number of other countries.