China correctly declared that it was within its sovereign rights to dredge, and that it was merely following the lead of its neighbors, whose governments had also been creating structures to bolster their claims. But American suspicions were heightened by the fact that in 2013, in a separate dispute between China and Japan over the Senkaku/Daiyou Islands in the East China Sea, the Chinese government unilaterally declared an Air Defense Identification Zone without prior warning.