Turkish president Recep Tayyip Erdogan on Friday said the Kurdish-held Afrin region in north-west Syria had to be cleared of "terrorists", days ahead of a summit meeting with Russia and Iran on Syria's future.
Mr Erdogan has repeatedly threatened to launch a military operation on Afrin, which is controlled by the Peoples' Protection Units (YPG) considered by Turkey to be a terror group.
But the YPG has been the main ally of the United States in fighting ISIL Syria, a policy that has infuriated Ankara.
"Afrin needs to be cleared of the YPG terror group," Mr Erdogan said in a televised speech to his ruling AK Party, adding that Turkish troops needed to be deployed there as in Syria's Idlib province.
"Otherwise, different terror groups will occupy the area."
Ankara views the YPG as an extension of the outlawed Kurdistan Workers Party (PKK), which has fought a decades-long insurgency in Turkey and is designated a terrorist group by Turkey, the United States and European Union.
Mr Erdogan criticised the United States for supporting the YPG, saying former president Barack Obama had failed to keep his promises while under Donald Trump Washington had continued to cooperate with the same group under the name Syrian Democratic Forces (SDF).
"It was a big disappointment for us that America has not kept its promises, to a large extent, since the start of the Syrian crisis," the Turkish president said.
"We don't want to enter into the same game in Afrin. A problem that we could solve quite easily together as allies is being dragged out by American intransigence."
Turkey has watched from the sidelines as the SDF has recaptured areas including Raqqa city from ISIL.
Mr Erdogan also scoffed at the idea that the United States was fighting against ISIL.
"That's the headline. But what did you do? You paid a lot of dollars to Daesh," he said, reasserting a claim he has raised in the past that has been rubbished by Washington.
Ankara and Moscow announced on Thursday that Mr Erdogan and his Russian and Iranian counterparts Vladimir Putin and Hassan Rouhani would meet for a summit on Syria on November 22 in Sochi.
The three countries are now calling themselves the "guarantor powers" for Syria, with no mention of the United States.
"Turkey, Russia and Iran have reached the point of having a common stance" on Syria, Mr Erdogan said.
This was not always the case. Russia, along with Iran, is the key backer of Syrian president Bashar Al Assad. Turkey, however, has backed the rebels seeking to depose the Assad regime in a conflict that has left more than 330,000 dead.
But Russia and Turkey have been working together since a 2016 reconciliation deal ended a crisis caused by the shooting down of a Russian war plane over Syria.