Brett McGurk, U.S. special envoy for the global coalition to defeat Daesh, submitted his resignation on Friday, CBS reported on Saturday citing sources, ahead of his departure planned in February.
McGurk's resignation came as a result of "strong disagreement" with President Donald Trump's decision to pull U.S. troops out of Syria, CBS reported, and a day after Trump's Defense Secretary Jim Mattis quit on the back of same decision.
A U.S. State Department official later confirmed McGurk's resignation and said it will take effect from December 31.
McGurk worked under the past three administrations, becoming one of the few persons appointed by former President Barack Obama to keep his post under U.S. President Donald Trump. He also served under the Bush administration.
The envoy had originally planned to leave his post in 2019 but decided to accelerate his resignation over strong disagreements with Trump over the withdrawal of U.S. troops from Syria, the news channel reported quoting anonymous sources.
McGurk's resignation comes as a surprise because the envoy had told reporters at the State Department that the U.S. was going to remain committed to the fight against Daesh terrorist forces last week.
"Nobody is declaring a mission accomplished. Defeating a physical caliphate is one phase of a much longer-term campaign," McGurk told reporters.
McGurk sent in his resignation on Friday, a day after Secretary of Defense James Mattis quit saying his views were not aligned with the president. Mattis will end his post in February.
On Wednesday, Washington announced it will be withdrawing all of its troops from Syria, following a conversation between President Recep Tayyip Erdoğan and U.S. counterpart Trump over an imminent Turkish cross-border operation to eliminate PKK-affiliated People's Protection Units (YPG) from northern Syria.
It has been reported that the U.S. still has about 2,000 troops in Syria, many of whom are working in close cooperation with Syrian Democratic Forces (SDF).
Almost all the territory in the east of the Euphrates River comprising some one-third of the territory of Syria, except for the Assad regime-controlled area near Deir el-Zour and the Daesh-held area near the Iraqi border, is controlled by the SDF. The SDF also controls the districts of Manbij and Tabqah on the right bank of the river.
Due to the group's links with the PKK, Ankara has called the YPG-held areas a "terror corridor" and said repeatedly it will not allow the region to turn into an autonomous region administered by the terrorist group.