The U.S. State Department has called on other nations to repatriate and prosecute their citizens captured by U.S. Kurdish allies in Syria.
The Syrian Democratic Forces, an alliance of militias dominated by the Kurdish YPG, "has demonstrated a clear commitment to detain these individuals securely and humanely," the department's spokesman, Robert Palladino, said in a statement on February 4.
The alliance, known as the SDF, say they have detained more than 900 foreign fighters who had traveled to Syria to fight with the extremist group Islamic State.
They are also holding more than 4,000 family members of IS fighters.
Questions arose about what the SDF would do with the prisoners it is holding after President Donald Trump announced in December that the United States would withdraw all of its 2,000 troops from Syria.
Few countries have so far expressed any readiness to repatriate their citizens.
Washington is set to host a meeting on February 6 of about a dozen coalition partners fighting against the IS group.
IS militants have lost virtually all the territory they once held in Syria and neighboring Iraq, but Palladino said it remains "a significant terrorist threat.”
"Collective action is imperative to address this shared international security challenge," he added.