Turkish President Recep Tayyip Erdogan has warned that his country cannot handle a "new refugee wave" from Syria.
Tens of thousands of people have fled towards the Turkish border amid increased bombardment of the rebel-held Idlib province in north-west Syria.
Turkey already hosts some 3.7 million Syrian refugees - the largest refugee population in the world.
Mr Erdogan warned that a new influx would be "felt by all European countries".
Up to three million people live in Idlib province, the last major region in Syria still held by rebel fighters and jihadists opposed to President Bashar al-Assad.
What did Erdogan say?
Speaking at an awards ceremony in Istanbul on Sunday, Mr Erdogan said more than 80,000 people from Idlib had fled to areas near the Turkish border amid heightened bombardments from Syrian and Russian forces.
"If the violence towards the people of Idlib does not stop, this number will increase even more. In that case, Turkey will not carry such a migrant burden on its own," he said.
"The negative effects of this pressure on us will be an issue felt by all European countries, especially Greece," he added.
The Turkish president warned of a repeat of the 2015 migrant crisis - when more than a million people fled to Europe - if the violence did not end.
He said a Turkish delegation was set to go to Moscow on Monday to discuss the situation.
A ceasefire negotiated by Russia and Turkey halted a Syrian government assault on Idlib in August. But skirmishes and bombardments are still an almost daily occurrence.
What does Turkey want to happen?
Turkey wants Syrian refugees to return to a "safe zone" in the north-east of Syria that was seized from Kurdish-led forces in October.
Mr Erdogan has called for support for the plan, saying he would otherwise be forced to "open the gates" for Syrians to enter Europe.
Turkey's offensive in northern Syria drew widespread international condemnation, and its safe zone plan has had little backing from allies.
"We call on European countries to use their energy to stop the massacre in Idlib, rather than trying to corner Turkey for the legitimate steps it took in Syria," Mr Erdogan said on Sunday.