Moscow said on Sunday that U.S. moves east of the Euphrates in northern Syria aim to establish quasi-state structures in the areas controlled by the PKK-affiliated People's Protection Units (YPG) and violate the territorial integrity of the country.

"Unacceptable things are happening on the eastern bank of the Euphrates river. The U.S. is trying to establish quasi-state structures; they earmark hundreds of millions of dollars into rebuilding these areas, so that people can return to a normal peaceful life, but they refuse to restore infrastructure in the territories, which are controlled by the Syrian government," Russian Foreign Minister Sergey Lavrov said in an interview with a Russian TV Channel, Tass reported.

"This is a very dangerous game, taking into account that the Kurdish issue is vital in a whole number of regional states [in Syria, Iraq, Iran and Turkey]," he added.

The YPG functions under the Syrian Democratic Forces (SDF), which is heavily backed by Washington under the pretext of fighting Daesh. Turkey sees no difference between the PKK, a group also listed on U.S. and EU terror lists, and the YPG in Syria, as the two groups are organically linked and have fluid movement of members between their lines.

Currently, the YPG controls approximately 25 percent of Syrian territory and nearly 65 percent of the 900-kilometer border with Turkey. "What is happening on the eastern bank of the Euphrates river clearly violates the commitment to Syria's territorial integrity, declared by all and confirmed in the U.N. Security Council's resolution. In my view, this is already evident for all," Lavrov stressed.

Last week, issuing a press statement following the end of the first day of the 11th round of the Astana talks, Russia's special envoy to Syria Alexander Lavrentiev said that the U.S. is using Daesh as an excuse to justify its presence in northern Syria and its cooperation with the YPG.

"In a small region located on the Syrian-Iraq border, there are about 1,000-1,500 remaining [Daesh] terrorists. Compare that with the 60,000 YPG military forces the U.S. is using the fight against Daesh to maintain its presence in Syria," Lavrentiev said.