U.S. admiral warns that China has fully militarized three islands in South China Sea

At least three artificial islands in the contested South China Sea have been fully militarized by China, threatening all nearby nations, a top U.S. admiral warned Sunday.

Although Beijing promised that the islands it built would not be used for its military, the U.S. Indo-Pacific commander Adm. John C. Aquilino said the areas are armed with "anti-ship and anti-aircraft missile systems, laser and jamming equipment and fighter jets," the Associated Press reported.

"I think over the past 20 years we’ve witnessed the largest military buildup since World War II by the [People's Republic of China]," Aquilino told the AP. "They have advanced all their capabilities and that buildup of weaponization is destabilizing to the region."

Beijing did not immediately comment on the matter to AP. Chinese officials have contended before that their military is purely defensive.

However, after years of increased spending, China is now second only to the United States in its military budget. The Communist country increased its defense budget earlier this month and is expected to spend about $270 billion on its military this year, Voice of America reported. China is also rapidly modernizing its military with new technology and weapons systems. 

The AP interviewed Aquilino on a U.S. Navy reconnaissance aircraft near outposts held by China in the South China Sea. AP reporters witnessed China call on the U.S. aircraft to issue a warning.

"China has sovereignty over the Spratly islands, as well as surrounding maritime areas. Stay away immediately to avoid misjudgment," the Chinese official warned. 

The U.S. aircraft stood its ground. 

"I am a sovereign immune United States naval aircraft conducting lawful military activities beyond the national airspace of any coastal state," an American pilot radioed to the Chinese.

"Exercising these rights is guaranteed by international law and I am operating with due regard to the rights and duties of all states," he added.

China protests any U.S. military involvement in the South China Sea, which the communist country claims to have nearly full sovereignty over. Meanwhile, the Philippines, Vietnam, Malaysia, Taiwan and Brunei claim to control all or part of the sea as well.

Aquilino said it seems as though China has finished constructing missile arsenals, radar systems, aircraft hangars and other military facilities on three manmade islands in the sea, but China may continue to build up its military in other areas.

"The function of those islands is to expand the offensive capability of the PRC beyond their continental shores," Aquilino told the AP. "They can fly fighters, bombers plus all those offensive capabilities of missile systems."

The United States says the main goal in the region is to "prevent war," but Aquilino stressed that "[s]hould deterrence fail, my second mission is to be prepared to fight and win."