Turkey's President Recep Tayyip Erdogan has threatened to launch an operation in Syria's Idlib region by the end of the month if Damascus fails to withdraw behind Turkish military positions.
"An operation in Idlib is imminent," Erdogan told his party's legislators in Parliament on Wednesday. "We are counting down, we are making our final warnings."
Russia - the Syrian government's main ally in the nearly nine-year war - responded by saying any Turkish offensive against Syrian forces in Idlib would be the "worst scenario".
"If we are talking about an operation against the legitimate authorities of the Syrian Republic and armed forces of the Syrian republic this would, of course, be the worst scenario," said Kremlin Press Secretary Dmitry Peskov, adding Russia and Turkey were staying in contact to prevent tensions escalating further.
Ankara, which backs several rebel groups in northwest Syria, has been outraged since recent Syrian government attacks in Idlib province killed 13 Turkish military personnel in two weeks.
Al Jazeera's Hashem Ahelbarra has more from Hatay.