Turkish Prime Minister Binali Yildirim said Saturday he believes Syrian President Bashar al-Assad is beginning to view as a "threat" Kurdish forces in the north who are backed by the United States and battling Islamic State.
Yildirim also said his government would be "more active" in the next six months in Syria, without specifying further.
Forces loyal to al-Assad have been battling with the Kurds in recent days around the northern Syrian city of al-Hassakeh and the government has launched airstrikes against them for the first time, earning it a strong rebuke from the US.
The US scrambled jets to al-Hassakeh on Thursday after the airstrikes and a spokesman warned Washington reserved the right to self-defence, as it has special forces based in northern Syria.
"The Syrian regime would be well-advised not to interfere with coalition forces or our partners," Defense Department spokesman Jeff Davis said.
The US has been partnered with the Syrian Kurds since late 2014 in a campaign against Islamic State.
Ankara is irked by the partnership, fearing increased nationalist sentiment among its own Kurdish minority and the links between the People's Protection Units (YPG) in Syria to the Kurdistan Workers' Party (PKK) in Turkey.
Analysts say recent YPG gains against Islamic State in northern Syria, close to the border, have made Turkey's concerns about the group more acute.
The Kurds in both Turkey and Syria have for decades complained of systemic discrimination.
For most of the war, the YPG and the Syrian government have managed to make tacit agreements and avoid direct conflict.
Al-Assad abandoned most Kurdish areas in the north in the early stages of the civil war and the YPG has begun to carve out autonomous zones.
In a harsh statement released late Friday, the Syrian army said the Kurds carried out "acts of provocation," including stealing cotton and oil, and accused the Kurdish militia of being a wing of the PKK, something al-Assad's government normally avoids.
The statement also pledged to ensure Syria's territorial integrity. Yildirim told reporters he too opposed dividing Syria along ethnic lines – though Ankara and Damascus rarely agree.
Ankara is a key backer of rebel groups fighting al-Assad, including facilitating arms shipments, according to Syrian factions.
The Syrian civil war has evolved into multiple conflicts inside the country between various rebel factions, al-Assad, the Kurds and Islamic State as well as foreign powers, including Turkey, Gulf Arab nations, Iran, Russia and the United States.