Top US envoy in fight against IS group resigns

His resignation, effective December 31, comes just after Donald Trump abruptly ordered the withdrawal of US troops from Syria as well as the announcement that Defense Secretary Jim Mattis was quitting, citing key disagreements with the US president.

Just last week McGurk, a Barack Obama appointee who Trump kept on, said "nobody is declaring a mission accomplished" in the battle against IS - just days before the president's stunning announcement of victory against the jihadist movement.

Trump - who postponed his holiday vacation as failed budget talks triggered a partial US government shutdown - again on Saturday said "ISIS is largely defeated."

"When I became President, ISIS was going wild," the president tweeted. 

McGurk reportedly said in his resignation letter that IS militants were in fact not defeated, and that prematurely withdrawing US troops could foster conditions allowing the jihadists to amass power in the region once more.

The 45-year-old top envoy was set to leave his position in February, but reportedly felt he could no longer continue in the job after Trump's declaration.