HONG KONG • China's apparent construction of a third airstrip on its man-made islands in the disputed South China Sea could fill a gap in Beijing's anti-submarine defences, complicating operations for the United States Navy and its allies, Chinese and Western experts said.
While most attention has been on the power projection China would get from its new islands in the Spratly archipelago, China could also use them to hunt rival submarines in and beyond the strategic waterway, they said.
Possessing three airstrips more than 1,400km from the Chinese mainland would enable Beijing to extend the reach of Y-9 surveillance planes and Ka-28 helicopters that are being re-equipped to track submarines, the experts added.
A Pentagon report in May noted China lacked a robust anti-submarine warfare capability off its coastline and in deep water.
Strengthened anti-submarine capabilities could also help China protect the movements of its Jin-class submarines, capable of carrying nuclear-armed ballistic missiles and which are at the core of China's nuclear deterrence strategy, said Professor Zhang Baohui of Hong Kong's Lingnan University.
"That would provide greater security for China's nuclear submarines to survive... and if necessary to execute their orders in wartime," Prof Zhang said. "They would be safer than in open oceans where China cannot provide adequate support."
The artificial islands, built on seven reefs over the last two years, will be high on the agenda when Chinese President Xi Jinping has talks with President Barack Obama in Washington next week.
Washington has criticised the reclamation and construction.
China, increasingly confident about its military firepower, has repeatedly stressed it has "indisputable sovereignty" over the entire Spratlys, saying the islands would be used for civilian and undefined military purposes.
Foreign Minister Wang Yi on Wednesday said "necessary" construction work would improve conditions on the islands.
Satellite photographs show construction is almost finished on a 3,000m long airstrip on Fiery Cross Reef.
Recent images showed Subi Reef would also have a 3,000m airstrip, Mr Greg Poling, director of the Asia Maritime Transparency Initiative at the Centre for Strategic and International Studies think-tank in Washington, said on Monday. He said China also appeared to be doing preparatory work for an airstrip on Mischief Reef.
Together, the three islands form a rough triangle in the heart of the Spratlys, where the Philippines, Vietnam, Malaysia, Brunei and Taiwan all have competing claims.
Asked if Washington was concerned the airstrips would enhance China's anti-submarine capabilities, a Pentagon spokesman, Commander Bill Urban, said the US was monitoring events in the South China Sea.
In a speech on Wednesday, US Defence Secretary Ash Carter said the US would "fly, sail, and operate wherever international law allows".