The Russian Foreign Ministry stressed on Tuesday that the US decision to establish military bases in the country to "secure" the Syrian oil fields is illegitimate, as doing so violates international law.
"Any actions that aim to bolster the illegal military presence of the United States [in Syria] go against the international law and are unacceptable from our point of view", Deputy Foreign Minister Sergei Vershinin told reporters.
American troops pulled back from several areas as Ankara launched its Operation Peace Spring on 9 October, commencing an offensive against Daesh* terrorists and the US-backed Syrian Democratic Forces (SDF).
Washington and the European Union slammed the decision, introducing sanctions against Ankara, but the Turkish government continued the operation in order to create a so-called safe zone near its territory in order to keep out the SDF, which it considers to be affiliated with the Kurdistan Workers' Party (PKK), banned in the country.
Kurdish forces had to withdraw from the Syria-Turkey border, later arranging a deal with Damascus, which subsequently bolstered its forces in the northern part of the country.
The crisis eased after Russian President Vladimir Putin and his Turkish counterpart Recep Tayyip Erdogan agreed to establish joint patrols on the border, while Moscow also vowed to ensure that the Kurdish-led forces would retreat from the Turkish border.
At the same time, Washington and Ankara negotiated a ceasefire between the Turkish Army and the Kurdish militia in the region, which later became permanent.
* Daesh (ISIL/ISIS/IS/Islamic State) is a terrorist organisation banned in Russia