Turkish President Recep Tayyip Erdogan is due to meet President Trump in New York on the sidelines of this week's United Nations General Assembly. The meeting, possibly on Wednesday, comes as Turkey is threatening to move further into Syria to attack Kurdish militia forces, a key American ally. The two NATO members also remain at odds over a number of other differences, including Ankara's decision to buy a Russian missile system. Dorian Jones has this preview from Istanbul.