Binali Yildirim, the Turkish prime minister, met James Mattis, the US defence secretary, before the announcement to discuss his position on Syria

Turkey vowed to make the United States reverse its decision to arm Kurdish fighters in Syria yesterday, threatening to intensify its fight against Kurdish separatists on both sides of its border.

Binali Yildirim, the Turkish prime minister, said Turkey was ready to step up its fight against the Syrian Kurds, despite Washington’s decision to directly arm them for the fight to retake the Islamic State stronghold of Raqqa.

“We are fighting against them inside our borders and if they are outside our borders in Iraq and Syria, we will fight them there as well,” Mr Yildirim told reporters in London a day after meeting James Mattis, the US defence secretary, to discuss the announcement.

“They are not humans, they are machines killing humans,” he said.