"[The US authorities are] working with the coalition on foreign-fighter detainees and generally expect these detainees to return to their country of origin for disposition," Wheelbarger said Sunday, as quoted by DefenseNews outlet.
The Pentagon official stressed that the countries from which the fighters originated needed to organize their domestic resources to "try to find a country by country ability to keep these folks both off the battlefield and out of our cities."
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According to Wheelbarger, the numbers of captured Daesh fighters are straining the jailing capacities of the Syrian Democratic Forces (SDF) militias.
"There are certain days we’re seeing 40-50 a day being captured. So the capacity problem is real. I haven’t heard from the SDF [about] a timeframe problem. I think they are willing to hold them as long [as needed] but it's more the volume, especially if they continue to capture them at the rates that they are," Wheelbarger was quoted as saying.
US Secretary of Defense James Mattis is expected to address the issue at the meeting of the anti-Daesh coalition in Rome on Tuesday.
The US has been fighting against Daesh in Syria since 2014 both without the approval of the government or a UN mandate.