Emmanuel Macron has hit out at Donald Trump’s decision to withdrawal US troops from the conflict in Syria, saying “an ally should be dependable”.

The French president said that he “deeply regretted” the decision to abruptly change a pillar of US foreign policy in the region by bringing home the 2,000 troops.

Mr Trump’s decision, announced on Wednesday, has alarmed US allies both in the Middle East and Europe with the president having declared victory over the jihadi group Isis.

Both US defence secretary James Mattis and the US envoy to the coalition fighting Isis, Brett McGurk, have resigned in the wake of the move.

“I very deeply regret the decision made on Syria,” Mr Macron said during a news conference in Chad.

“To be allies is to fight shoulder to shoulder. It’s the most important thing for a head of state and head of the military,” he said. “An ally should be dependable.”

Mr Mattis had said in his resignation letter that the president needed a defence secretary whose views “better aligned” with his own. Mr Mattis also reiterated that America should use all the alliances at its disposal – including Nato – to ensure America is kept safe.

Mr McGurk described Mr Trump’s decision as a “shock” with experienced national security personnel having made clear that while Isis had been significantly weakened, they could still pose a threat.

Only 11 days ago, Mr McGurk had said it would be “reckless” to consider Isis defeated and therefore would be unwise to bring American forces home.

"War of Annihilation" – devastating toll on civilians in Raqqa, Syria Show all 20 1 /20 "War of Annihilation" – devastating toll on civilians in Raqqa, Syria "War of Annihilation" – devastating toll on civilians in Raqqa, Syria A child injured by an IED explosion in Raqqa Amnesty International "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Children riding a bicycle among destroyed buildings in Raqqa Amnesty International "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Entire neighbourhoods in Raqqa are damaged beyond repair Amnesty International "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Satellite image showing the house where seven members of the Badran family were killed in a Coalition strike on 18 July 2017, before the strike CNES/Airbus DS "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Satellite image showing the house where seven members of the Badran family were killed in a Coalition strike on 18 July 2017, after the strike CNES/Airbus DS "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Members of the Badran family killed in three separate Coalition air strike on 18 July and 20 August 2017 in Raqqa Amnesty International "War of Annihilation" – devastating toll on civilians in Raqqa, Syria The city of Raqqa in northern Syria has become hardly recognizable to those who try to return after months battle between US-backed forces and the Islamic State terrorist group for control of it. The city has no running water or electricity and homes, business and public squares are mere rubble and debris Amnesty International "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Satellite image showing the houses where 16 members of the Fayad family and neighbours were killed in Coalition strikes on 12 October 2017, before the strike CNES/Airbus DS "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Satellite image showing the houses where 16 members of the Fayad family and neighbours were killed in Coalition strikes on 12 October 2017, after the strike CNES/Airbus DS "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Fayad Mohammed and his daughters Wafa’, Fadda and Tamam; Ammar al-Faris; Reem al-Maddad, Yusra Abd-al-Aziz, and baby Razqiya Habib; Jasim Hamal and Salem Hamad. They were among the 16 civilians killed in Coalition air strikes on 12 October 2017 in Raqqa Amnesty International "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Men wait by the side of the road for casual labour in Raqqa. Many end up clearing partially destroyed or damaged buildings, a very risky endeavour as many building were mined by IS and civilians are frequently killed and injured by mines Amnesty "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Satellite images showing the Aswad family’s building before it was destroyed in a Coalition air strike which killed eight civilians, five of them children, on 28 June 2017 CNES/Airbus DS "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Satellite image showing the Aswad family’s building after it was destroyed in a Coalition air strike which killed eight civilians, five of them children, on 28 June 2017 CNES/Airbus DS "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Amal Othman, 13, and her brothers Ammar, 8 and Mahmoud, 17; and Jamal Aswad, 41 – four of the eight victims killed in a Coalition air strike on 28 June 2017 in Raqqa Amnesty International "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Low-income district west of the Jezra intersection on the western outskirts of Raqqa city destroyed by the Coalition shelling started in June 2017 Amnesty International "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Satellite image showing the houses where 16 members of the Fayad family and neighbours were killed in Coalition strikes on 12 October 2017, before the strike CNES/Airbus DS "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Satellite image showing the houses where 16 members of the Fayad family and neighbours were killed in Coalition strikes on 12 October 2017, after the strike CNES/Airbus DS "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Ali Hassan Nafa; Mahdia Hashish and her husband Hussein Ali; Hussein Hashish, Mohammed Hashish and Hussein Ibrahim Hashish, and Mohammed Ali Hashish Amnesty International "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Harat al Badu, a built up area in central Raqqa, next to the stadium. It was the scene of the final battle in the city between SDF/Coalition forces and IS Amnesty International "War of Annihilation" – devastating toll on civilians in Raqqa, Syria Map showing where the Badran, Hashish, Aswad and Fayab families were living before the coalition air strikes Unosat /Amnesty International

Mr McGurk, who was appointed by former president Barack Obama in 2015, has decided to speed up his original plan to leave the Trump administration in February.

“The recent decision by the president came as a shock and was a complete reversal of policy,” he said in an email to his staff viewed by The Associated Press.

Mr Trump’s announcement of the withdrawal “left our coalition partners confused and our fighting partners bewildered with no plan in place or even considered thought as to consequences,” the email went on.

Mr Trump and the White House have sought to play down the departure of Mr McGurk amid mounting international unease. The president tweeted on Saturday night: “I do not know” the envoy. He added that it was a “nothing event” and called Mr McGurk a “grandstander”.

Mr Trump’s acting chief of staff, Mick Mulvaney, told ABC’s This Week on Sunday morning: “I have no idea who that person is. Never heard of him... until yesterday”.

In his press conference on Sunday, Mr Macron pointed out the debt the international coalition owes to the Kurdish-led Syrian Democratic Forces (SDF), who have captured large parts of northern and eastern Syria from Isis with support from the US and other partners.

“I call on everyone... not to forget what we owe them,” Mr Macron said.

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With the US withdrawal, the Kurdish-led forces fear military action by Turkey, with its president Recep Tayyip Erdogan having vowed to take out the SDF, whom Ankara views as an extension of the Kurdish insurgency within its borders.

On Sunday, it was reported by local media and a war monitoring group that Turkey is amassing troops near a town in northern Syria held by the SDF. The build-up comes despite recent promises by Turkey to postpone an offensive into northern Syria in the wake of the US troop withdrawal decision.

Turkey already has troops in northwestern Syria and has backed Syrian fighters there to clear towns and villages of Isis militants and Kurdish fighters.

The Turkish IHA news agency reported a commando unit of troops had been sent into Syria overnight. The Syrian Observatory for Human Rights said the reinforcements, numbering dozens of vehicles, were sent to the frontline with Manbij, where US troops have been based.

Mr Trump tweeted on Sunday afternoon that he spoken by phone with Mr Erdogan claiming they discussed “Isis, our mutual involvement in Syria, & the slow & highly coordinated pullout of US troops from the area”.