WASHINGTON, DC, USA (AP) — US troops are scrambling for Syria’s exits while the Trump Administration threatens economic penalties on Turkey for an invasion that opened the door to a resurgence of the Islamic State (IS) group — fighters who were the reason US forces came in the first place.

The Turks began attacks in Syria against the Kurds, long-time US battlefield allies against IS, after President Donald Trump declared US troops would stay out of the fight.

American troops consolidated their positions in northern Syria yesterday and prepared to evacuate equipment in advance of a full withdrawal as Turkish forces pressed an offensive against the Kurds, a US defence official said.

The preparations, triggered by Trump’s decision Saturday to expand a limited troop pull-out into a complete withdrawal, came as Trump’s national security team considered imposing what he called “big sanctions” on North Atlantic Treaty Organisation (NATO) ally Turkey.

The US pull-out raised many questions, including how and whether the Trump Administration would continue putting military pressure on the Islamic State in Syria without a troop presence on the ground. US forces have been there since 2015, arming and advising a Kurdish-led Syrian group of fighters who largely eliminated IS control of Syrian territory but were still working to prevent an IS resurgence.

The defence official, who was not authorised to be quoted by name, said US officials were weighing options for the future of a counter-IS campaign, including the possibility of waging it with a combination of air power and special operations forces based outside of Syria.

Defence Secretary Mark Esper said Sunday that Trump had directed US troops in northern Syria to begin pulling out “as safely and quickly as possible”. He did not say Trump ordered troops to leave Syria, but that seemed like the next step in a combat zone growing more unstable by the hour.

Esper said the US withdrawal would be done carefully to protect the troops and to ensure that no US equipment was left behind. He declined to say how long that might take.

Trump defended his gamble that pulling US forces out of Syria would not weaken US security and credibility. He wrote on Twitter yesterday that the Islamic State prisoners who have escaped amid the pandemonium in Syria can be “easily recaptured” by Turkey or European nations, even as France said it was pulling its remaining troops out of Syria.

“Big sanctions on Turkey coming!” Trump wrote, and his treasury secretary, Steven Mnuchin, said that while no final decision on sanctions had been made, the president’s national security team was meeting again to consider a way ahead.

Esper, interviewed on two TV news shows, said the Administration was considering its options.

“We have American forces likely caught between two opposing advancing armies, and it’s a very untenable situation,” Esper said.

This seemed likely to herald the end of a five-year effort to partner with Syrian, Kurdish and Arab fighters to ensure a lasting defeat of the Islamic State group. Hundreds of IS supporters escaped a holding camp amid clashes between invading Turkish-led forces and Kurdish fighters, and analysts said an IS resurgence seemed more likely, just months after Trump declared the extremists defeated.