WASHINGTON - The US Defence Department revealed that China's total land reclamation area in the South China Sea has quadrupled over about four months, expressing concern that the move could be aimed at creating "persistent civil-military bases of operation."
An annual report on military and security developments related to China, released Friday, mentioned for the first time the nation's reclamation of land around rocks and reefs in the South China Sea.
A Pentagon official told reporters on the day that the total acreage of the reclaimed area - described as two square kilometers in a report last December - had grown to about eight square kilometers.
The area in question is equivalent to about 170 times the size of Tokyo Dome. According to the report, China has been undertaking the reclamation at five outposts on the Spratly Islands, which it calls the Nansha Islands.
The report clearly indicated the US Defence Department's alarm, saying China aims to "significantly enhance its presence in the disputed area."
Adm. Harry Harris, the commander of the US Pacific Command, described the reclamation as the building of "a Great Wall of sand," speaking in March.
China's accelerating moves to change the status quo in the South China Sea have raised anxiety in the United States.
Without naming specific reefs, the report states that as of last December, "China transitioned from land reclamation operations to infrastructure development" at four of the five outposts.
According to its analysis, China has set up harbors, communications and surveillance systems, logistic support facilities, and at least one airfield in the reclaimed area.
China, which has already developed a heliport on Gaven Reef, is believed to have begun constructing a runway on Fiery Cross Reef.
At the time of the report's release, a Pentagon official criticised China's moves, saying the large-scale reclamation is incompatible with the region's desire for peace and stability.
The report also stated that China has been using "low-intensity coercion" in the East China Sea and South China Sea to claim sovereignty. This includes trade tariffs, tourism restrictions and limits on foreign direct investment, as well as the dispatch of fishing boats.
"China often uses a progression of ... steps to increase its effective control over disputed territories and avoid escalation to military conflict," the report said.
In addition, the report expressed alarm over the rapid modernization of China's military power, saying it could potentially reduce the US forces' core technological advantage.
The report also said China is investing in capabilities to deter the deployment of adversary forces and counter interventions by third parties - including the United States - in the event of a crisis or conflict.
The report said the Chinese military's Second Artillery Force, which is in charge of ballistic missiles, is developing and testing new classes of hypersonic and other offensive missiles.
US bases in Japan are within the range of an increasing number of medium-range ballistic missiles and ground-attack cruise missiles, and Guam is likely within the range of air-launched cruise missiles, according to the report.
Regarding nuclear weapons, the report concluded it is highly likely that China's Jin-class nuclear submarine - carrying Julang-2 submarine-launched ballistic missiles - will begin its first patrols for nuclear deterrent purposes by the year-end.