Trump says Turkey's Erdogan will 'eradicate whatever is left of' Islamic State in Syria

US President Donald Trump said Monday that Turkish President Recep Tayyip Erdogan will "eradicate whatever" is left of Islamic State in Syria. 

Trump had said last week that Islamic State had been defeated in Syria, which is why he was pulling US troops out of the country. 

"President @RT_Erdogan of Turkey has very strongly informed me that he will eradicate whatever is left of ISIS in Syria....and he is a man who can do it plus, Turkey is right 'next door'," Trump tweeted Monday. 

"Our troops are coming home!" he added. 

Trump seemed to be referring to an earlier phone call with President Erdogan during which they agreed not to leave behind a power vacuum after US forces leave. The US has some 2,000 troops at the moment in Syria. 

Trump's decision to pull out of Syria has been met by shock around the world. 

Trump's Secretary of Defence General Jim Mattis resigned over the shock move. 

So did Brett McGurk, America's envoy to the US-led coalition fighting Islamic State. News reports have described McGurk as the glue that bound the coalition together. 

Turkey has been among a handful of countries to encourage Trump's decision to pull out of Syria (the others have included Russia and Syria). But that is because Turkey has been keen to go after the Kurds in northern Syria. The Kurds had been fighting alongside the US coalition but Turkey thinks of them as terrorists. 

Commentators have also said Trump's decision to pull out of Syria is political. 

That it and Trump's doubling down over his demand for funding for his border wall with Mexico will keep his base happy. 

And that it will also shine some of the spotlight away from the various investigations into Trump and his 2016 presidential campaign's alleged collusion with Russia.