The United States is justified in carrying out surveillance flights in East Asia, in spite of Chinese objections, given a lack of transparency in China's military buildup, a senior US official said on Friday.
Beijing called last month for the United States to cut back, or even stop, close surveillance by patrol aircraft if it seriously sought to repair damaged bilateral ties.
The request followed an Aug. 19 incident in which Washington said a Chinese jet flew dangerously close to a US navy P-8 Poseidon anti-submarine and reconnaissance plane operating in international waters southeast of the Chinese island of Hainan.
Asked about the Chinese call to scale back such flights, Assistant Secretary of State Daniel Russel, the senior US diplomat for East Asia, pointed to China's big military buildup in recent years and the secrecy surrounding it.
"We have the right to conduct legitimate missions outside of China's territorial space and there is a persuasive rational for doing so," he told Reuters.
"Frankly, the lack of transparency in China's military modernization is the source of some concern to its neighbours. And we believe that all of the region, including China, would benefit from increased transparency."
Russel pointed to aggressive Chinese moves to press territorial claims in the South China Sea, including accelerated land reclamation work on reefs and shoals, and said these were a cause of anxiety for other countries in the region.
He said that while Beijing rightly pointed out it was not the only claimant to have carried out such work, "the pace of China's reclamation in the sensitive disputed waters of the South China Sea vastly outstrips what other claimants have done in the past by many orders of magnitude."
Russel said China's reclamation activity had proved "intimidating and worrisome" to its neighbours.
"It's generating questions and concerns in the region -
is China planning to build military bases; is China using reclaimed land on these shoals for the purpose of extending its reach and trying to create a de-facto answer to the question of who has sovereignty of the various land features?" he said.
Russel declined to give his view as to what China's plans were, but said: "What I think the effect of what they are doing is to destabilize the situation and make it harder, not easier, for the claimants to resolve their claims peacefully."
Beijing argues that "high-frequency, close surveillance" by US patrols has seriously harmed its security interests.
Last month's incident took place 220 km (137 miles) from Hainan, which is home to several military bases, including one that houses a sensitive submarine fleet.
Among the submarines using the base are large Jin-class vessels capable of carrying nuclear-armed ballistic missiles that are expected to form a key plank in China's nuclear deterrence strategy.