Rome - The US wants to see foreign fighters being held by Syrian Democratic Forces turned over to their home countries.
US officials worry that facilities in Syria will eventually be filled to capacity if the detainees aren't returned to their home countries for disposition.
Among the thousands of Islamic State fighters held by the US-backed SDF are hundreds of fighters from several nations.
A State Department official says the US is working with its coalition partners on the problem and expects most of the detainees to be returned home.
US Defense Secretary Jim Mattis is expected to raise the issue of detained foreign fighters when he meets in Rome this week with other members of the coalition that is fighting the Islamic State group in Iraq and Syria.