The US has started withdrawing its troops from Syria, an American military spokesman said on Friday, further muddling the Trump administration’s plans for disengagement from one of West Asia’s most complex battlefields.

As recently as Sunday, President Trump’s national security adviser, John R. Bolton, had said that the pullout was conditional on circumstances that could leave American forces there for months or even years. That followed by less than a month with Trump’s announcement that he intended to pull out the roughly 2,000 American troops within 30 days.

The surprise announcement came in a statement from Col Sean Ryan, the spokesman for the US-led coalition against the Islamic State. Col Ryan said the coalition had “begun the process of our deliberate withdrawal from Syria”, adding that he would provide no further information about “specific timelines, locations or troop movements”.

But the announcement, coming days after Bolton’s remarks, added to a climate of chaos surrounding Washington’s policy on Syria at a time when Turkey has threatened to invade the country.

Trump has made no secret of his desire to bring the troops home, saying that they were sent to fight the Islamic State and that their mission has nearly been accomplished. In an apparently snap decision following a telephone call with the Turkish President, Recep Tayyip Erdogan, he said last month that he wanted the troops out within a month.

That decision prompted the resignation of two top aides — defence secretary Jim Mattis and Brett McGurk, the special presidential envoy to the coalition fighting the Islamic State — and the reformulation by Bolton, a hawkish adviser whose principle West Asia aim is to contain the ambitions of Iran, which is entrenched in Syria.

Reflecting the confusion, Interfax reported that the spokeswoman for the Russian foreign ministry, Maria Zakharova, said in Moscow on Friday that the American military’s announcement added to the Kremlin’s growing doubts that the US would soon withdraw from Syria.

It seems like Washington “is looking for a reason to stay”, she said. “I cannot share your confidence that they are leaving there because we never saw an official strategy.

After Trump’s call for a rapid pullout, discussions with others in his administration led to the timeline being lengthened as diplomats sought to find a way to protect the US’ Kurdish allies from a Turkish attack and to get Turkey to take over the fight against the extremists.

The possible swift withdrawal of the American troops posted in northern and eastern Syria alarmed many analysts, who warned that could threaten to hinder the Islamic State and unleash a potentially violent scramble between the other forces in Syria to fill the void.

The US had intervened in Syria to work with local, Kurdish-led militias to fight the Islamic State.

The Syrian government and its Russian and Iranian allies want the territory back for several reasons: its oil deposits; its agricultural land; reopening the border with Iraq; and reunification of the country, which has been shattered by a war that began in 2011.