According to the sources, the commanders told Trump that pockets of the IS terrorists "remained in the Euphrates River valley and that US military had not yet eliminated all of their strongholds".

Trump was informed that the US military successfully took back other areas from the IS but the job is yet to be finished.

The sources stressed that the officers' remarks were "eye-opening" for Trump, who earlier claimed that the IS was "badly" defeated in Syria, announcing the start of US withdrawal from the state.

On Wednesday, Vice President Mike Pence claimed that the IS had indeed been defeated, adding that the US is "now able to hand off the fight against IS to our coalition partners" after the group's caliphate "crumbled."

Earlier that day, a spokesperson for Operation Inherent Resolve announced in a tweet that several US service members had been among the 16 people killed in a bomb attack in the northern Syrian town of Manbij. The IS reportedly claimed responsibility for the bombing.

In December, Trump signalled the White House's plans to withdraw roughly 2,000 US troops from Syria within the next several months.

The decision was slammed by some US officials and prompted two resignations: US Secretary of Defence Jim Mattis, who stressed that his views were no longer aligned with Trump's, and Brett McGurk, special presidential envoy for the US coalition in Syria.

Reporter’s code: 50101