Ground operation in Syria's Afrin has "actively" begun, Turkish President Recep Tayyip Erdogan said on Saturday, according to Anadolu agency.

Addressing the ruling Justice and Development (AK) Party's sixth annual provincial congress in western city of Kutahya, Erdogan said an operation in Manbij in Syria will come after Afrin because "promises made to Turkey have not been kept."

He criticized the United States for working with the Kurdistan Workers' Party (PKK). "They know it really well. They are trying their best to deceive Turkey and the world." Erdogan also said Turkey will "clear terrorism that tries to encircle the country up to Iraqi border".

To note, the Turkish government considers Kurdish militias in Syria to be an extension of the militant movement PKK which is seen as a terrorist organization by Ankara.

Last week’s news that Washington was training the predominantly Kurdish Syrian Democratic Forces (SDF) to form a 30,000-strong “border force” based in Afrin infuriated the Turks. The US has since backtracked on the announcement in an apparent attempt to defuse Turkish anger, but belligerent statements from Ankara have continued.

Meanwhile, the Syrian government warned on Thursday that it may shoot down Turkish warplanes delivering airstrikes on its territory. Damascus said its air defenses have been restored and are ready to defend the nation’s sovereignty.