|The US has seen Chinese activity around a reef China seized from the Philippines nearly four years ago that could be a precursor to more land reclamation in the disputed South China Sea.|
China's claims raise fears Beijing will declare an exclusion zone in the busy trade route. China claims most of the South China Sea, through which more than $5 trillion in global trade passes every year.
| Vietnam, Malaysia, Brunei, the Philippines and Taiwan have rival claims. Head of U.S. naval operations Admiral John Richardson said the United States was weighing responses to such a move.|
| China could respond to an expected ruling by the court of arbitration in The Hague by declaring an air defense identification zone, or ADIZ, as it did to the north, in the East China Sea, in 2013.|
On Wednesday China reported it is building a tsunami alert center in the South China Sea.