The order has been signed for the withdrawal of American troops from Syria, where they had been deployed to assist in the war against the Islamic State group, a US military spokesperson has said.
"The execute order for Syria has been signed," the spokesperson told AFP, without providing further details.
US President Donald Trump has declared the jihadist group "largely defeated" and made the surprise decision to bring US forces home.
Many US politicians and international allies fear the move is premature and would further destabilise the already devastated region.
Turkey's President Recep Tayyip Erdogan and President Trump have agreed in a phone conversation to prevent a power vacuum in Syria after US ground forces withdraw.
I just had a long and productive call with President @RT_Erdogan of Turkey. We discussed ISIS, our mutual involvement in Syria, & the slow & highly coordinated pullout of U.S. troops from the area. After many years they are coming home. We also discussed heavily expanded Trade.
— Donald J. Trump (@realDonaldTrump) December 23, 2018
Analysts said the withdrawal of US troops will leave the Kurdish forces, who are members of the Syrian Democratic Forces or SDF, vulnerable.
Turkey has sent military reinforcements to Northern Syria close to an area controlled by Kurdish forces, which were backed by US troops.
French President Emmanuel Macron has criticised President Trump's decision, saying "an ally must be reliable".
Read more:
- Trump orders full withdrawal of US troops from Syria
- Trump defends US withdrawal from Syria, says others must fight
