The United States' envoy to the global coalition battling the Islamic State group has quit.
It is believed this is over President Donald Trump's decision to withdraw US troops from Syria, with a CBS source citing a "strong disagreement" over the matter.
A US State Department official confirmed on Saturday that Brett McGurk, special envoy for the global coalition to defeat ISIS, has handed in his resignation.
The 45-year-old joins Defence Secretary Jim Mattis in an exodus of experienced national security officials.
Just 11 days ago Mr McGurk said it would be "reckless" to consider ISIS defeated and unwise to bring American forces home.
It is believed his resignation letter was submitted on Friday to Secretary of State Mike Pompeo.
Mr McGurk was appointed to his post by President Barack Obama in 2015 and retained by President Trump.
His resignation is effective from December 31.
He was previously planning to leave the job in mid-February after a US-hosted meeting of foreign ministers from the coalition countries.
However, he felt he could continue no longer after Trump's decision to withdraw from Syria and Mr Mattis' resignation.
President Trump is acting to pull all 2,000 US troops from Syria and has now declared victory over the Islamic State, contradicting his own experts' assessments.
Mr Mattis, perhaps the most respected foreign policy official in the administration, announced on Thursday he will leave by the end of February.
He told President Trump in a letter that he was departing because "you have a right to have a Secretary of Defence whose views are better aligned with yours".
Earlier this week, Mr Trump released a video message on Twitter to announce the surprise decision.
“We have won against ISIS [Islamic State],” said the President.
“We’ve beaten them and we’ve beaten them badly. We’ve taken back the land and now it’s time for our troops to come back home. I get very saddened when I have to write letters or call parents or wives or husbands of soldiers who have been killed fighting for our country. So our boys, our young women, our men, they’re all coming back and they’re coming back now. We won, and that’s the way we want it.”
