"We are doing all the necessary preparations to clean the other side of the border because of the problems in Kilis," Erdogan said amid persistent speculation of a possible Turkish cross-border ground operation, without giving details on the preparations.
Around two dozen people have been killed in the Turkish border town of Kilis by rocket fire from IS jihadists since January, prompting the army to respond with artillery fire.
Turkey, a member of the US-led coalition battling IS, also allows US jets to use its air base in southern Turkey for air strikes on the extremists.
But Erdogan complained that Turkey was not receiving the support it desired from its allies in the fight against IS and indicated Ankara was prepared to take unilateral action.
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"While our citizens fall martyr every day in the streets of Kilis by rockets launched from the other side, what can we expect from our allies?" he said.
"Let me say it here. We will not hesitate to take needed steps on our own if necessary," he said.
Turkish media reports have indicated a 20-strong Turkish military team crossed into Syria over the weekend on a reconnaissance mission to seek out IS launchers to target in artillery strikes, but this has not been officially confirmed.
Erdogan said what happens in Kilis would be a "litmus test" to show the anti-IS coalition's sincerity in dealing with the threat.
"We do not believe the sincerity of any country that has not seen rockets falling on our town as if they fell on Moscow, London, Brussels, Washington, Paris or Berlin," he said.