"We have 2,500 [IS] fighters that we want Europe to take because they were going back into Europe - into France, into Germany, into various places," Trump said on Thursday. "And let’s see if they take them. And if they don’t take them, we’ll probably have to release them to Europe."

Trump said overall the United States captured more than 10,000 prisoners after defeating the IS caliphate.

The issue of who will retain long-term custody of IS former fighters deemed too dangerous to release remains an unresolved one between the US government and its European allies.