HK GOT INT,L STRATEGIC CONSULTING LIMITED

BEIJING — China is building a concrete runway on an island in the South China Sea’s contested waters that will be capable of handling military aircraft when finished, satellite images released Thursday show.

The first section of the runway appears like a piece of gray ribbon on an image taken last month of Fiery Cross Reef, part of the Spratly Islands, an archipelago claimed by at least three other countries. Adjacent to the runway, work is underway on an apron for taxiing and parking planes.

The runway, which is expected to be about 10,000 feet long — enough to accommodate fighter jets and surveillance aircraft — represents a game changer in the competition between the United States and China in the South China Sea, said Peter Dutton, professor of strategic studies at the Naval War College in Rhode Island.

“This is a major strategic event,” Mr. Dutton said. “In order to have sea control, you need to have air control.”

Analysts had speculated that China planned to build an airstrip on Fiery Cross Reef, but the satellite image from March 23, provided by Airbus and released Thursday by Jane’s Defense Weekly, is the first hard evidence that it is doing so.

In time, Mr. Dutton said, China is likely to install radar and missiles that could intimidate smaller countries like the Philippines, an American ally, and Vietnam, which also have claims to the Spratlys, as they resupply their modest military garrisons in the area.

More broadly, he said, China’s ability to use Fiery Cross Reef as a landing strip for fighter and surveillance aircraft will vastly expand its zone of competition with the United States in the South China Sea.

Over the past decade and a half, a series of tense encounters between American and Chinese forces on the sea and in the air — starting with a near collision in 2001 between an American EP-3 spy plane and a Chinese fighter — have occurred in the sea’s northern waters, near China. The new installations in the Spratlys, about 1,000 miles beyond China’s southernmost point on Hainan Island, will create a much wider arena for potential close calls, Mr. Dutton said.

“This will expand the area in which there are likely to be tensions between the United States and China,” he said.

The construction on Fiery Cross Reef is part of a larger Chinese reclamation project involving scores of dredgers on at least five islands in the South China Sea. China is converting tiny reefs, once barely visible above water, into islands big enough to handle military hardware, personnel and recreation facilities for workers.

Satellite images of the reclamation efforts have been released in steady doses over the last few months, as smaller countries with claims to islands in the area have voiced concern about China’s accelerated construction, and as the United States has stepped up its criticism.

During his recent first trip to Asia as the American defense secretary, Ashton B. Carter said in Japan that the reclamation efforts were seriously aggravating tensions between Beijing and Washington and hurting the prospects for diplomatic solutions.

After Mr. Carter made those remarks, the Center for Strategic and International Studies, a Washington research group, released images of Mischief Reef, also in the Spratly archipelago, that showed large-scale dredging of sand and coral to create land mass on what had been a partly submerged reef.

The construction on Fiery Cross Reef, which is several hundred miles west of Mischief Reef, appears to have taken place within the last several weeks. An image taken by Airbus on Feb. 6, also released Thursday by Jane’s Defense Weekly, shows empty sand where the runway is now being built.

“We absolutely think it is for military aircraft, but of course an airstrip is an airstrip — anything can land on it if it’s long enough,” said James Hardy, Asia-Pacific editor for Jane’s Defense Weekly. “Three thousand meters is big enough for pretty much any aircraft,” he said, noting that the superjumbo Airbus A380’s runway requirement is 2,950 meters, or just under 10,000 feet.

Other runways used by the Chinese military have ranged from around 8,850 feet to more than 13,100 feet, he said. By comparison, the runway maintained by the United States Air Force at Diego Garcia, an island in the Indian Ocean that is much bigger and more developed than Fiery Cross Reef, is 11,800 feet, he said.

“The main question is, What else would land there?” Mr. Hardy said. “Unless they are planning to turn these into resorts — which seems unlikely, not least given the statement from the Foreign Ministry last week — then military aircraft are the only things that would need to land there.”

China’s Foreign Ministry said in a statement last week that the reclamation efforts were intended to serve civilian purposes, such as providing a base for search-and-rescue operations, but also for “satisfying the need of necessary military defense.” Though the statement placed more emphasis on the nonmilitary goals, it was a rare acknowledgment of Chinese military intentions in the South China Sea.

Mr. Hardy said that China’s military appeared to have chosen Fiery Cross Reef as a command-and-control center for its Spratly Islands operations.

China claims more than 80 percent of the South China Sea, on the grounds that a so-called nine-dash line drawn around the waterway by China in the late 1940s conforms to China’s rights in the sea. No other country recognizes the validity of the nine-dash line, and many fear that China’s reclamation activities are part of a drive to create an inevitability about Chinese ownership.

In another example of the Pentagon’s heightened criticism of China’s reclamation efforts, a senior Navy commander, Rear Adm. Christopher J. Paul, said last month in Australia that there are countries “who attempt to constrict movement through international waters, who create land areas where there were none; who create exclusion zones where there should be shared use.”

In response, he said, the Navy was creating “hunter-killer surface action groups” of ships, and he suggested that Australia, one of America’s staunchest allies, would be invited to contribute to the new efforts in offensive naval warfare.