"We regret the US support for this step that ignores international law and that targets Syria's territorial integrity and sovereignty," Turkish foreign ministry said in a statement. By calling the agreement "unacceptable", the ministry also pointed out that the deal would finance terrorism in the conflict-ravaged region.
Turkey on Monday blasted an agreement between YPG/PKK militants in Syria's northeast and a US oil company as "unacceptable" and equivalent to terrorism financing.
Senior Washington officials have confirmed that a US oil company has signed an agreement with the YPG-led Syrian Democratic Forces (SDF) to "modernise" oil fields under its control.
Syria already condemned the deal as "theft" and an "affront to (its) national sovereignty" on Sunday.
The SDF is a YPG-led paramilitary alliance that backs a semi-autonomous administration in northeastern Syria and controls the country's biggest oilfields.
The US-backed SDF is mostly made up of the YPG which Turkey considers to be a "terror group" linked to the bloody-minded PKK.
The Turkish foreign ministry said the name of the US company was Delta Crescent Energy LLC, according to press reports.
"We regret the US support for this step that ignores international law and that targets Syria's territorial integrity and sovereignty," the ministry said in a statement.
By calling the agreement "unacceptable", the ministry pointed out that the deal would finance terrorism in the region.
The foreign ministry accused the YPG militant group of advancing "its separatist agenda by confiscating, with this step, Syrian people's natural resources."
"Syria's natural resources belong to Syrian people," it added.
US Senator Lindsey Graham, a longtime supporter of the YPG/PKK, told Congress on Thursday that he had spoken to YPG-led SDF commander General Mazloum Abdi about the deal.
Asked by Graham if the US was supportive of the deal, Secretary of State Mike Pompeo said: "We are."
The US support for YPG in Syria has become one of the stumbling blocks in bilateral ties between the two NATO allies.
The Turkish military has launched three cross-border into Syria to fight Daesh/ISIS terrorists and the YPG/PKK militants./aa