- Video report by ITV News Washington Correspondent Robert Moore
Donald Trump's decision to pull US troops out of Syria will lead to a resurgence in Islamic State extremism, a key American ally has warned.
The Kurdish-led Syrian Democratic Forces said a premature US troop pullout would have dangerous repercussions and risk destabilising the region.
Mr Trump's sudden decision has not only rattled foreign allies, it has angered some closer to home. US Defence Secretary Jim Mattis stepped down from his post after clashing with the president over his decision to pull troops in Syria.
The repercussions of Mr Trump's decision are keenly felt by Kurds who see it as a betrayal. The withdrawal of troops will leave them dangerously exposed to attacks from the Syrian regime and Turkey with President Recep Tayyip Erdogan repeatedly threatening to launch a new offensive against them.
With US air support, the Kurds drove IS from much of northern and eastern Syria in a costly four-year campaign.
Mr Trump's contention that IS has been defeated contradicted his own experts' assessments and shocked his party's politicians, who called his decision rash and dangerous.
One world leader did support US withdrawal. Russia's Vladimir Putin called American involvement in Syria "illegitimate", declaring Mr Trump's decision the "correct move".
The US began air strikes against IS in Syria in 2014, and later sent in ground troops to aid Kurdish forces.
Mr Trump abruptly declared their mission accomplished in a tweet on Wednesday, and defended his decision on Thursday.
He tweeted: "Does the USA want to be the Policeman of the Middle East, getting NOTHING but spending precious lives and trillions of dollars protecting others who, in almost all cases, do not appreciate what we are doing? Do we want to be there forever?"
Mr Trump said his decision in Syria should be "no surprise", adding: "I've been campaigning on it for years."