Chinese and American officials began talks Monday aimed at ending a bruising tariffs battle between the world's two biggest economies, as Beijing complained over the sighting of a U.S. warship in what it said were Chinese waters.

China's placement of weapons systems on manmade islands in the South China Sea is designed to intimidate and coerce others in the region, Defence Secretary Jim Mattis said Saturday, laying out a sharp criticism of Beijing at an international security forum.

The operation was the latest attempt to counter what Washington sees as Beijing's efforts to limit freedom of navigation in the strategic waters.