Chinese Weapons Spotted on Disputed Island, U.S. Says

The United States has spotted a pair of mobile artillery vehicles on an artificial island that China is building in the South China Sea, a resource-rich stretch of ocean crossed by vital shipping lanes, American officials said.China’s construction program on previously uninhabited atolls and reefs in the Spratly Islands has already raised alarm and drawn protests from other countries in the region, whose claims to parts of the South China Sea overlap with China’s.

Defense Secretary Ashton B. Carter called this week for China to halt the construction, saying that international law did not recognize Chinese claims of sovereignty over the new territories and that American warships and military aircraft would continue to operate in the area.The artillery was spotted by satellites and surveillance aircraft about a month ago, and the two vehicles have since been either hidden or removed, according to an American official who spoke about intelligence matters on the condition of anonymity. The official added that even if the weapons remain on the island, they pose no threat to American naval forces or aircraft in the region, though the guns could reach some nearby islands claimed by other countries.

With Mr. Carter in Singapore to attend the Shangri-La Dialogue, a high-profile annual Asian security meeting that Chinese officials are also attending, American officials were reluctant to publicly discuss the intelligence they had collected about the artillery.Brent Colburn, a spokesman traveling with Mr. Carter, would say only that the United States was aware of the weapons, whose detection was first reported by The Wall Street Journal.

Senator John McCain, the Arizona Republican who heads the Senate Armed Services Committee, criticized China’s deployment of artillery on the island as “a disturbing development and escalatory development.”

“Their actions are in violation of international law, and their actions are going to be condemned by everyone in the world,” Mr. McCain was quoted by Reuters as saying in Ho Chi Minh City, Vietnam, where he stopped on Friday on his way to Singapore for the security conference.“We are not going to have a conflict with China,” he said, “but we can take certain measures which will be a disincentive to China to continue these kinds of activities.”There was no immediate comment from Chinese officials about the weapons.

China has said that it was building the artificial islands largely for civilian purposes, but it has not hidden the fact that it also envisions a military role for them.In April, Hua Chunying, the spokeswoman for China’s foreign ministry, told reporters that the islands would be used to aid the country’s defense, though she did not provide details. “Such constructions are within China’s sovereignty and are fair, reasonable, lawful and do not affect nor target any country, and are beyond reproach,” she said.The United States disagrees, and American officials have stressed in recent days that the American-dominated security order in the region should be respected because it has brought calm and prosperity.

The implication is that China is threatening to upend that system, but the American officials have hesitated to say so directly, preferring to talk in generalities about all countries needing to find diplomatic solutions to their disputes in the South China Sea.Still, American officials have not been shy about pointing out that China has created roughly 2,000 acres of new land in the South China Sea, three quarters of it this year. The United States has also released video images taken by surveillance aircraft showing Chinese ships and dredges building runways and harbors on remote outcroppings in the sea.