Donald Trump has told the EU it must take back its 800 Isis fighters captured in Syria by US-backed forces and put them on trial.

The president’s call came as he prepared to claim the end of the caliphate in north-west Syria with the fall of the final Isis-held town.

Some EU countries, notably France, have said they are preparing to take back their former jihadists, but the UK has been more resistant: it says the fighters held by the west’s Syrian Kurd allies can only return if they seek consular help in Turkey.

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The UK government says it faces a dilemma, especially concerning the wives or children of British fighters, and a major challenge either to prosecute the fighters or prevent them from undertaking terrorist acts in their homeland.

Trump tweeted: “The United States is asking Britain, France, Germany and other European allies to take back over 800 Isis fighters that we captured in Syria and put them on trial. The Caliphate is ready to fall. The alternative is not a good one in that we will be forced to release them.

“The US does not want to watch as these Isis fighters permeate Europe, which is where they are expected to go. We do so much, and spend so much - Time for others to step up and do the job that they are so capable of doing. We are pulling back after 100% Caliphate victory!”

Diplomats gathered at this weekend’s Munich security conference, a major meeting of officials and policymakers, have repeatedly warned that the capture of Isis-held territory does not mean an end to the Isis ideological and terrorist threat; they point to the way in which Isis forces are already regathering in Iraq, notably Mosul.

The Syrian Democratic Forces (SDF) say they have cornered the remaining Isis militants in a neighbourhood of Baghuz village near the Iraqi border. Foreign fighters and families have featured prominently among those who have fled the village, which had been been a collection point for extremists who had fled other towns and villages across Syria and Iraq. It is thought to be the last redoubt of zealots who had fought in numerous clashes across both countries.

A SDF spokesman on Sunday said Isis militants were preventing more than 1,000 civilians from leaving. Shamima Begum, 19, one of three east London schoolgirls who left the UK in 2015 to join Isis, was on Thursday discovered in the al-Hawl refugee camp in north-east Syria after fleeing the enclave.

Trump’s remarks mask an intense transatlantic debate under way between politicians and military over how to handle his unilateral decision to withdraw its 2,000 troops in north-west Syria.

The US military, and Arab states, have been pressing the Trump administration to delay the move to give more time for an agreement to be reached on how the mainly Kurd SDF are to be protected from a potential Turkish incursion once US forces leave.

The Turkish defence minister, Hulusi Akar, met his US counterpart, Patrick Shanahan, on the sidelines of the Munich conference to press his plan for Turkey to establish a safe zone, saying the Kurds in the SDF are indistinguishable from the Kurdish PKK fighting a separatist terrorist war inside Turkey. The Kurdish leadership is resisting the move, fearing it will lead to either a massacre or displacement of the Kurds.

“There is no difference between the PKK and the YPG,” Akar said. “A 440-km-long (273-mile) safe zone in east of Euphrates should be cleared of the terrorist YPG group and should be patrolled by the Turkish forces,” he stressed.

In a speech broadcast on Syrian state television, Bashar al-Assad said his troops would “liberate every inch” of the country and warned Kurdish forces not to rely on US protection. “To those groups who are betting on the Americans, we say the Americans will not protect you... the Americans will put you in their pockets to be used as bargaining tools,” he said.

James Jeffery, US envoy for Syria, said it “will not allow the return of the Assad forces to the places where we will withdraw them from.[…] this is not going to be an abrupt, rapid withdrawal but a step-by-step withdrawal.”

There is growing frustration in European and Gulf states at what they regard as the incoherence of US policy making in Syria both in substance and method.

Senior Republican senators such as Lindsey Graham have acknowledged that the SDF has borne the brunt of fighting Isis, and there would be long term implications for the US’s reputation in the Middle East if it was seen to desert its allies at this stage.

He said Trump had been pressing European forces to set up a small international force to protect the Kurds, including some of the foreign fighters currently held by Kurds either in jails or, in the case of their relatives, in refugee camps. France has as many as 400 forces in Syria, but the UK foreign secretary, Jeremy Hunt, said in an interview published in the Arab press in the weekend that the UK has no plans to send further forces to the region, but will listen to any US request.

Joe Biden a potential Democratic presidential candidate urged Europe to wait for the return of a consultative America. Describing current US foreign policy as an embarrassment, he said: “We will be back”.

Ilham Ahmed, the executive chair of the political wing of the SDF, has been touring Washington, Paris and London to press the case for an international force.

Some Gulf states have said privately they are willing to help provide financial and practical support to such a force, including one effectively led by the Kurds themselves, so long as it is part of a wider UN political process that leads to a long term settlement.

These Gulf states say the Kurds deserve a place in a more federated future Syria, something Assad would resist.

The Gulf States are slowly moving towards recognition of Assad – such as the United Arab Emirates, which has has set up an embassy again in Damascus. The Gulf States believe that, along with the UK, they will have to pick up the eventual cost of Syria’s reconstruction on the basis that Syria, Russia and Iran will be unable to afford such a large bill.