Turkey "will not shoulder [the refugee burden] on its own," Erdogan said, adding that "all European countries, Greece in particular, will feel the negative impact."
Turkey says it hosts 3.7 million Syrian refugees.
"It is then inevitable to see scenes similar to before March 18," Erdogan said, referring to a 2016 deal between Turkey and the EU under which Ankara has agreed to curb migration to Europe.
The EU in return agreed to send financial aid to Syrian refugees in Turkey.
Erdogan has recently warned he will "open the gates" to Europe for Syrian refugees, criticizing the bloc for failing to send enough financial support.
Syrian government forces on Saturday seized more territory in Idlib, the country's last rebel stronghold, state media reported, as part of a Russia-backed campaign that has displaced thousands of civilians.
Around 72,000 civilians have been displaced by the violence since early December, the Syrian Observatory for Human Rights, a war monitor, reported on Saturday.
Turkey will continue talking to Russia to help end the attacks on Idlib, Erdogan said, adding Ankara will "determine its own steps" following negotiations with Moscow.
-----------------------------------------------------------------------------------------------------