The United States considers the Syrian Kurdish militia the most effective force against the Islamic State group in Syria, but Turkey considers the force a terror organisation because of its affiliation to Turkey's outlawed Kurdish rebels.

In his weekly address to his ruling party legislators on Tuesday, Binali Yildirim questioned the morality of "fighting a terrorist organisation with another terrorist organisation."

Clinton said during Sunday's debate with Donald Trump that she favoured continuing the Obama administration's practice of funneling weapons to Iraq's Kurdish armed forces and also hinted that she would consider extending that support to Syrian Kurdish fighters.