The Kurdish-led administration in northern Syria has called for the creation of an international court to try thousands of suspected members of the Islamic State (IS) group.
One official, Abdul Karim Omar, told the BBC they were struggling to cope with the thousands who emerged from the last IS enclave of Baghuz, in the east.
Kurdish-led Syrian Democratic Forces (SDF) captured the village last week.
About 1,000 foreign fighters are among the thousands held by Kurds in camps.
US President Donald Trump hailed the capture of Baghuz last week, although he said the US would “remain vigilant” as the group remains a threat.
At its height, IS controlled 88,000 sq km (34,000 sq miles) across Syria and Iraq.
While it no longer holds this territory, US officials believe IS may have 15,000 to 20,000 armed adherents active in the region, many of them in sleeper cells, and that it will return to its insurgent roots while attempting to rebuild.
In a statement, the Kurdish administration called for “a special international tribunal in north-east Syria to prosecute terrorists” to ensure that trials are “conducted fairly and in accordance with international law and human rights covenants and charters
Speaking to the BBC, the administration’s head of foreign affairs, Abdul Karim Omar, said the fact so few nations had repatriated their citizens who joined IS has added to their problems.
The administration has struggled to cope with even detaining the militants it has captured, let alone putting them on trial, says the BBC’s Aleem Maqbool in Syria.
Many Western governments have refused to repatriate their citizens amid concerns over the potential security risks they may pose, as well as the challenges of gathering evidence to support prosecutions.
Women and children are kept in camps for the displaced.
According to one Kurdish official speaking to AFP, more than 9,000 foreign relatives of IS members – many of them children – are being held at the Kurdish-run al-Hol camp.
The accommodation was built for about 20,000 people but is now housing more than 70,000.
US envoy for Syria James Jeffrey told reporters on Monday the focus was on repatriating militants, and “getting countries to take back their own foreign terrorist fighters”.
Iraqis and Syrians should be sent home “for deradicalisation and reintegration or in some cases punishment”, while countries around the world should be encouraged to “take back their own citizens”.
Asked if the US was considering an international tribunal, Mr Jeffrey said: “We’re not looking at that right now.”
There have been several international tribunals in the past, including to try war crimes in the Balkan conflicts of the 1990s and after the Rwandan genocide in 1994.
But transitional justice expert Joel Hubrecht told AFP news agency that it was “not realistic” to set up such a court in Syria.
Syria’s Kurdish authorities are not internationally recognised, and ensuring proper justice in a war-torn country is difficult, he added.