“The formation of a terrorist army along our border with Syria would cause irreversible damage to our ties with the US,” Çavuşoğlu said.
Speaking to Turkish broadcaster CNN Turk in an interview, Çavuşoglu also said the US did not keep its promises on Manbij and Raqqa and added that their mistrust toward the US was continuing.
He said Turkey wants to see concrete steps from the US on ending cooperation with "terrorist groups."
Çavuşoğlu also said the Syrian government's advance into Idlib needs to be stopped.
He added that the Syrian Kurdish People’s Protection Units (YPG) will not attend a meeting in Sochi, where a solution to the Syrian civil war will be sought.
Çavuşoğlu urged Russia to not oppose a Turkish military operation in Syria's Afrin, adding that they will coordinate with Moscow on the situation with Russian observers there.
“We are also discussing with Russia and Iran about the use of airspace. We need to coordinate this for a possible aerial intervention. This needs to be coordinated well in order to prevent any accidents from happening,” he said.
Çavuşoğlu did not specify the date of the possible Afrin operation but said that the Turkish military stated that they were ready to begin anytime.