Updated

The United States is urging allied nations to help deal with the growing number of foreign fighters that are being held by the U.S.-backed Syrian Democratic Forces. The U.S. says the militants should be turned over to face justice in their home countries.

U.S. Defense Secretary Jim Mattis is expected to raise the issue during a meeting in Rome this week with other members of the coalition fighting the Islamic State in Iraq and Syria.

The issue gained added urgency after the announcement that the SDF had captured two notorious British members of an Islamic State cell who were commonly dubbed the Beatles and were known for beheading hostages.

U.S. officials don't want them sent to Guantanamo Bay, while British leaders have suggested they don't want them returned to Britain.