Donald Trump Demands European Allies Take Back 800 Captured ISIS Fighters or 'We Will Be Forced to Release Them'

US President Donald Trump waves as he boards Air Force One at Andrews Air Force Base, MD, on February 15, 2019. Getty Images

President Donald Trump in a tweet Saturday night called on European nations to "take back" 800 fighters captured from the Islamic State militant group (ISIS) and put them on trial, warning that the U.S. would be withdrawing from the battle after its "100% Caliphate victory."

Trump also suggested that the U.S. would "be forced to release them" as an alternative if the U.S.'s European allies did not take control of the prisoners.

In a set of tweets, the president said: "The United States is asking Britain, France, Germany and other European allies to take back over 800 ISIS fighters that we captured in Syria and put them on trial. The Caliphate is ready to fall. The alternative is not a good one in that we will be forced to release them.

"The U.S. does not want to watch as these ISIS fighters permeate Europe, which is where they are expected to go. We do so much, and spend so much - Time for others to step up and do the job that they are so capable of doing. We are pulling back after 100% Caliphate victory!"

The message comes as U.S.-backed Syrian forces are poised to seize control of ISIS's last stronghold, the town of Baghuz, which is on the Syrian side of the border with Iraq.

Jiya Furat said the Syrian Democratic Forces (SDF) had cornered remaining ISIS fighters in a neighbourhood of Baghuz. "In the coming few days, in a very short time, we will spread the good tidings to the world of the military end of Daesh," he told Reuters, using the Arabic acronym for ISIS.

Trump had on Friday tweeted that the defeat of ISIS would be announced in the next 24 hours, but Furat said that fighters were holding civilians as human shields, slowing efforts to retake the town.

With the Caliphate on the brink of collapse, hundreds of civilians and ISIS fighters have surrendered themselves to SDF forces.

Among the civilians to have fled the town is British teenager Shamima Begum, 19, who is pregnant with the child of an ISIS fighter and was found by a Sunday Times reporter last week in al-Hawl refugee camp in northeastern Syria. She fled East London to join the Caliphate when she was 15 years old, along with two other teen girls. She has now expressed a desire to return to Britain.

U.K. Home Secretary Sajid Javid has warned that he "will not hesitate" to prevent her return to the country—a stance seemingly at odds with Trump's call for captives to be repatriated by European allies. It is not yet clear how Britain could refuse to allow Begun to return, as this would render her stateless.

In December, Trump announced that the U.S. would be withdrawing its forces from Syria, sparking the resignation of Defense Secretary James Mattis, with critics claiming the move could leave the U.S.'s Kurdish allies exposed to attack, allow ISIS to regain a foothold in Syria and create a power vacuum.

US President Donald Trump waves as he boards Air Force One at Andrews Air Force Base, MD, on February 15, 2019. Getty Images