"We are aware of reports that China has conducted civilian test flights at Fiery Cross Reef. We are concerned that these test flights have exacerbated tensions and are inconsistent with the region's commitments to exercise restraint from actions that could complicate or escalate disputes," the Pentagon said.
The US, it said, encourages all claimants to actively reduce tensions by refraining from unilateral actions that undermine regional stability and to take steps to create space for meaningful diplomatic solutions.
China for the first time landed a plane on an artificial island it has built in a contested part of the strategic South China Sea, prompting Vietnam to accuse Beijing of "serious infringement" of its sovereignty.
Yesterday, Chinese foreign ministry spokeswoman Hua Chunying said China conducted a "test flight" to check whether the newly-built airfield facilities met the standards for civil aviation. There were, however, no details given about when it was conducted.