Senior US officials have confirmed that an American oil company has signed an agreement with the Syrian Democratic Forces (SDF) to "modernize" Syria’s biggest oilfields under its control, AFP wrote.
Syria already condemned the deal as "theft" and an "affront to (its) national sovereignty" on Sunday.
The "null and void" deal is "a continuation of the US hostile approach toward Syria" by "stealing the resources of the Syrian people and hindering the efforts of the Syrian state to rebuild what has been destroyed by terrorism that is mostly backed by the US government itself," the Syrian Foreign Ministry said in a statement.
The US-backed paramilitary alliance is mostly made up of Syrian Kurdish militia forces which Turkey considers to be a "terror group" linked to the outlawed Kurdistan Workers' Party (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.
It considered the deal to be "the financing of terrorism" and "unacceptable."
The Foreign Ministry said that Kurdish militia force is 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 Syrian Kurds, told Congress on Thursday that he had spoken to SDF commander 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 deal took a little longer ... than we had hoped, and now we’re in implementation.”
The US support for Kurds in Syria has become one of the stumbling blocks in bilateral ties between the two NATO allies.
The Turkish military has launched three incursions into Syria to “fight Daesh and the Syrian Kurdish militia force”.