Also Sunday, Erdogan's spokesperson responded to reports the US -led coalition would establish a 30,000-strong border security force in Syria involving the Kurdish militia as "worrying".
"The slightest disturbance on the border would be the signal for us to take a step", Mr Erdogan said in a televised speech.
A senior Syrian Kurdish official said on Sunday that fighting between the YPG and Turkish forces was already under way.
The U.S. -led worldwide coalition against Daesh will establish a 30,000-strong new border security force with the SDF - the U.S. -backed group that is largely controlled and manned by the PKK/PYD terrorist organization in Syria - a U.S. military official said Sunday.
It said that about 230 individuals were now undergoing training in the force's inaugural class.
Turkey and its Western allies, including the USA, consider the PKK a terrorist organization.
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YPG is considered by Turkey to be a "terrorist group" with ties to the banned Kurdistan Workers' Party (PKK), which has waged a decades-long insurgency inside the country.
A military source, who spoke on condition of anonymity due to restrictions on talking to media, said that the tanks were sent as reinforcements to the Turkish border units. "More Arabs will serve in the areas along the Euphrates River Valley and along the border with Iraq to the south". "It's absolutely not possible to accept this", Kalin said and repeated that Turkey would defend itself.
The Turkish forces were firing from Turkey's southern province Hatay and the observation point in Syria's Idlib province.
The president referred to Turkey's previous eight-month military operation launched in August 2016 against the Islamic State (IS) extremist group and the Syrian Kurdish Peoples' Protection Units (YPG) militia.
The US sees the YPG as the most effective fighting force against IS and a year ago provided it with arms ahead of major battles in Syria.
Listed as a terrorist organization by Turkey, the USA and the European Union, the PKK has waged a terror campaign against Turkey for more than 30 years, leading to the deaths of more than 40,000 security forces and civilians - including more than 1,200 since July 2015 alone, when it resumed its armed campaign against the Turkish state following a fragile cease-fire.