Trump discussed 'highly coordinated' US withdrawal from Syria with Erdogan

US President Donald Trump has said he has spoken with his Turkish counterpart Recep Tayyip Erdogan about the planned withdrawal of American forces from Syria.

The US president tweeted that the two leaders had "a long and productive call" about the Islamic State group and "heavily expanded trade." 

He also said the call involved discussions on "the slow & highly coordinated pullout of US troops from the area".

Trump shocked US allies on Friday when he announced plans to pull the 2,000 US troops out of Syria, a demand of Turkey.

They were there to help the Kurdish-led Syrian Democratic Forces defeat the Islamic State group, and have cornered them in the Hajin Pocket, in eastern Syria. 

The move would allow Turkish troops to move against the hardened Kurdish fighters in Syria deemed terrorists by the Ankara regime.

A US withdrawal, said Mutlu Civiroglu, a Kurdish affairs analyst, "will open way for Turkey to start its operations against the Kurds, and a bloody war will begin".

Defence Secretary Jim Mattis quit following Trump's announcement on the withdrawal of US forces from Syria, as did the US' leading Syria envoy Brett McGurk.

Trump also announced on Sunday that Patrick Shanahan would replace Mattis.

"I am pleased to announce that our very talented Deputy Secretary of Defense, Patrick Shanahan, will assume the title of Acting Secretary of Defense starting January 1, 2019," the Republican leader tweeted. 

"Patrick has a long list of accomplishments while serving as Deputy, & previously Boeing. He will be great!"