Tough Turkey talks await Tillerson

US Secretary of State Rex Tillerson faces "difficult" talks next week with NATO ally Turkey on Syria and human rights, his delegation said Friday before a regional tour.

Late last month, Ankara began a cross-border offensive in northwestern Syria against what it calls a "terrorist" Kurdish militia supported and armed by Washington whose troops are back local militias against the Islamic State group (IS).

The Turkish operation further raised tensions between the two countries, whose relations were already complicated.

"We are urging them to show restraint in their operations in Afrin, and to show restraint further along the line across the border in northern Syria," a senior US State Department official told reporters ahead of Tillerson's tour that begins Sunday.