China has militarized at most three of the islands it built in South China Sea. It also equipped them with anti-ship missile and anti-aircraft systems.

Adm. John C. Aquilino, the U.S. Indo-Pacific commander, stated that the hostile actions were completely in contrast to Chinese President Xi Jinping’s previous assurances that Beijing would not turn the artificial islands in contested water into military bases. He said that China was trying to flex its military muscles by making these efforts.

“I believe that over the past twenty years we’ve seen the largest military buildup by the PRC,” Aquilino stated to The Associated Press using the initials of China’s formal name. They have advanced all of their capabilities, and that building up of weaponization is destabilizing for the region.”

Chinese officials did not immediately respond to the request. Beijing claims its military profile is defensive and designed to protect its sovereign rights. After years of increasing military spending , China now has the second largest defense budget in the world. It is also rapidly modernizing its forces with weapons systems such as the J-20 stealth fighter and hypersonic missiles. A third carrier is currently under construction.

Aquilino spoke to the AP aboard a U.S. Navy reconnaissance plane that flew close to Chinese-held outposts in South China Sea’s Spratly Archipelago. One of the most contested regions in all of Asia. The Chinese called repeatedly to warn the P-8A Poseidon plane that it had illegally entered China’s territory. They ordered it to leave.

“China is sovereign over the Spratly Islands and surrounding maritime areas.” “Stop immediately to avoid misjudgment”, one of the stern radio messages stated in a veiled threat.

The U.S. Navy plane ignored all warnings and continued defiantly with its reconnaissance, in brief but intense moments that were witnessed by two AP journalists who were invited to board. A U.S. pilot radioed back to China, “I am a sovereign-immun United States naval aircraft conducting lawful militaristic activities beyond the national aviation space of any coastal states.”

He stated, “Exercising those rights is guaranteed under international law and I am operating in due regard to all rights and duties of other states.”

Joel Martinez, the Navy’s commanding officer, stated that there was an incident in which a Chinese plane flew too close to a U.S. jet in a dangerous maneuver in the disputed area. He said that the U.S. crew calmly reminded China to follow aviation safety regulations.

The P-8A Poseidon flew at 15,000 feet (4500 meters) above the Chinese-occupied reefs. Some of these cities looked like tiny cities on monitors. There were multi-story buildings, warehouses and hangars as well as runways and white-colored structures that Aquilino claimed were radars. More than 40 vessels were seen anchored near Fiery Cross.

Aquilino stated that the construction of missile weapons, aircraft hangars and radar systems on Mischief Reef, Subi Reef, and Fiery Cross appears to have been completed. However, it remains to see if China will continue to build military infrastructure in other areas.

He stated that “the function of these islands is to expand offensive capability of the PRC outside their continental shores.” They can fly fighters and bombers, as well as all the offensive capabilities of missile system.

He stated that any civilian or military plane flying over the disputed watersway could easily be within the range of the Chinese islands’ missile system.

He stated, “So that’s a threat that exists. That’s why it is so concerning for militarization of the islands.” They are a threat to all countries operating in the area, as well as all international air and seaspace.

China wanted to strengthen its enormous territorial claims in the South China Sea. It built islands bases on coral atolls almost a decade ago. The U.S. responded with warships that traversed the region on what it called freedom of operation missions. Although the United States does not claim this right, it has used Navy aircraft and ships for decades to promote freedom of navigation in international airspace and waterways.

China regularly objects to any U.S. military action in the region. The Philippines, Vietnam and Malaysia, Taiwan, Brunei, and Brunei claim part or all of the sea through which $5 trillion worth of goods is shipped each year.

Aquilino stated that despite China’s aggression, long-standing territorial disputes should be solved peacefully. He cited the example of the Philippine government’s 2013 successful attempt to submit its disputes to international arbitration.

The case was handled by an U.N.-backed tribunal, which invalidated China’s broad historical claims in the South China Sea. It also violated the U.N. Convention on the Law of the Sea. Beijing rejected the ruling and continues to challenge it.

Aquilino stated that Washington’s primary objective in the disputed area is to “prevent war” by deterrence, and promote peace, stability, and even engage American allies in projects with this objective.

Aquilino, who heads the largest U.S. combatant command, which has 380,000 military personnel and civilian personnel and covers 36 countries and territories, stated, “Should deterrence fail,”