The statement published by the White House earlier in the day said that the US special forces killed Abu Sayyaf, a senior commander at the Islamist State (ISIL) jihadist group, in a operation conducted with a prior consent of Iraqi authorities on Friday’s night.
"The U.S. government did not coordinate with the Syrian regime, nor did we advise them in advance of this operation," National Security Council spokeswoman Bernadette Meehan said as quoted by ITV.
She stressed that the Syrian government “is not and cannot be a partner in the fight against ISIL."
According to the White House, Abu Sayyaf was a senior ISIL leader who was involved in the group’s military operations and also was overseeing militants' illicit oil and gas operations.
His wife, Umm, suspected of being involved in the ISIL terrorist activities, was captured by US forces.
The Islamic State extremist group has seized vast territories across Syria and Iraq, gaining notoriety for its brutal methods, including mass executions.
A US-led coalition of some 60 nations has been carrying out airstrikes against the Islamic State targets in Iraq since August 2014, and in Syria since September 2014, albeit without the approval of the Syrian government.