The Syrian army is closing in on the last pockets of militant positions in Aleppo which borders Turkey, prompting an outcry among supporters of armed groups which are warning of a refugee influx.
Erdogan said on Thursday a no-fly zone is the only way to deal with the crisis, adding the problem could not be resolved without safe zones.
"We will show patience up to a point and then we'll do what's necessary. Our buses and planes are not waiting there in vain," he said.
Turkey has long pushed for the creation of a no-fly zone in northern Syria but the proposal has so far gained little traction with the US or NATO allies.
The US and Europe fear such a move could put them in direct confrontation with Russia and other allies of the Syrian government.
Erdogan accused the United Nations of insincerity in calling on Turkey to do more to help Syrian refugees instead of taking action to stop Russian airstrikes.
Russian war planes have been bombing areas around Aleppo in support of a Syrian government offensive to recapture the city.
"There is a chance that the new wave of refugees will reach 600,000 if airstrikes continue. We are making preparations for it," Erdogan said in a speech to a business forum in Ankara.
He said he had told EU's Jean-Claude Juncker and Donald Tusk that Turkey might open the gates for refugees to travel to Europe.
"In the past we have stopped people at the gates to Europe, in Edirne we stopped their buses. This happens once or twice, and then we'll open the gates and wish them a safe journey, that's what I said," he said.
A Greek news website said on Monday that Erdogan had threatened to flood Europe with refugees if EU leaders did not offer a better deal to Turkey.
On Wednesday, Erdogan accused the US of creating a "pool of blood" in the region by failing to recognize Kurdish organisations fighting Takfiris in Syria as terrorist groups.
Syria accuses Saudi Arabia, Turkey and Qatar of funding and arming terrorist groups operating inside the country, including Daesh.
The foreign-sponsored conflict in Syria, which flared up in March 2011, has reportedly killed more than 260,000 people and left over one million injured, Press TV reported.
S/SH 11