A 2015 satellite image of Mischief Reef in the disputed Spratly Islands in the South China Sea. Beijing has built 8,800 feet of runways on new airfields in the area. File Photo courtesy of CSIS Asia Maritime Transparency Initiative/DigitalGlobe
June 7 (UPI) -- China is expanding its presence in the South China Sea with new buildup on disputed islands, according to the Pentagon's 2017 survey of the Chinese military published Tuesday.
Beijing's People's Liberation Army Navy is also expanding its fleet of submarines and aircraft carriers.
China's submarine force is likely to grow to nearly 80 submarines by 2020, and Beijing's aircraft carrier Liaoning is expected to reach "initial operational capability" around that time, the annual report states.
But China's militarization of the disputed Spratly Islands in international waters is of greatest concern to the Pentagon.
U.S. Defense Secretary James Mattis recently criticized China's land reclamation activities in the disputed Spratly Islands, describing the activities as a demonstration of "China's disregard for international law" and its "contempt for other nations' interests."
China swiftly protested the statement, and accused the United States of harboring "ulterior motives."
The defense paper states China added 8,800 feet of runways on new airfields, after adding more than 3,200 acres of land across the Spratlys, including the Fiery Cross, Subi and Mischief Reefs.
"China was constructing 24 fighter-sized hangars, fixed-weapons positions, barracks, administration buildings and communication facilities at each of the three outposts," the report states.
Three regiments of fighter aircraft can be housed in the facilities.
The goal of making improvements to "military and civilian infrastructure in the South China Sea" is to "bolster de facto control" of the maritime region, according to the Pentagon.
The Chinese navy has also built 10 nuclear submarines since 2002. The four nuclear Jin-class submarines, the Type 094, can be equipped with submarine-launched ballistic missiles, or SLBMs, and more developments may be on course.
"China's next-generation Type 096 [nuclear-powered ballistic missile submarines], will likely begin construction in the early 2020s, and reportedly will be armed with the JL-3, a follow-on SLBM," the report states.
China retains a total of 63 submarines, including diesel-electric attack submarines and advanced, anti-cruise ship missile-capable submarines, according to the report.