A U.S. Navy warship was closely trailed by Chinese navy vessels in the South China Sea during a rare patrol close to where China has been dredging sand to turn submerged reefs and shoals into islands it claims as sovereign territory, according to the Pentagon.
China's close surveillance this month of the Fort Worth, a new high-tech San Diego-based littoral combat ship, suggested the growing tension over the competing maritime and territorial claims in the region's resource-rich waters.
The decision to send the Fort Worth near the Spratly Islands for the first time was intended to show Beijing that Washington does not accept that the surrounding seas constitute Chinese territorial waters. Navy officials said they plan to follow up with other patrols.
U.S. military officials, who worry that China is trying to establish de facto control over parts of a strategic international waterway, are formulating new options to present to President Obama. They include sending warships within 12 miles of the reclaimed reefs and rocks to make clear that Washington considers them international waters and is determined to preserve freedom of navigation.
Secretary of State John F. Kerry is expected to press U.S. concerns about the extensive landfill and construction projects, including potential runways and port facilities, when he meets top Chinese officials in Beijing this weekend.
For now, U.S. officials believe they can pressure China into scaling back its island-building by showing it is galvanizing other governments against it. In recent months the U.S. has encouraged Japan to begin naval patrols in the South China Sea, an area it has rarely ventured into, and provided ships and other equipment to the Philippine and Vietnamese coast guards.
The U.S. military also has stepped up operations. In January, the Navy began regular surveillance flights over the South China Sea, flying advanced P-8 Poseidon intelligence-gathering planes from a base in the Philippines.
The friction in the South China Sea is one of several security issues, including cybercrime, likely to dominate discussions as officials prepare for Chinese President Xi Jinping's first state visit to Washington this year.
But the White House is under pressure from U.S. lawmakers — and from some allies in the region — to take more aggressive steps to counter what some portray as potential Chinese threats to air and sea traffic far from its coastline.
Both nations are moving cautiously, at least in public. China's Foreign Ministry warned this week that it was "extremely concerned" about U.S. plans to add forces to the region.
"Freedom of navigation certainly does not mean that foreign military ships and aircraft can enter another country's territorial waters or airspace at will," spokeswoman Hua Chunying told reporters in Beijing.
Obama voiced concern last month in a White House news conference that China was "flexing its muscles" to advance its claims in the South China Sea as well as the East China Sea, where China and Japan claim a rocky island chain called Senkaku by Japan and Diaoyu by China.
China, the Philippines, Malaysia, Taiwan, Brunei and Vietnam all claim parts of the South China Sea in a dispute that has simmered for decades. Several nations are pursuing reclamation projects or have built small military installations on disputed islands.
But those projects are dwarfed by China's recent dredging. U.S. officials say the Chinese have created 2,000 acres of new land since last year on five coral outcrops in the Spratly archipelago: Fiery Cross Reef, Johnson South Reef, Johnson North Reef, Cuarteron Reef and Gaven Reef.
The U.S. believes it will take at least until 2017 for China to complete construction on what appears an airfield at Fiery Cross Reef, David Shear, assistant secretary of Defense for Asian and Pacific Security Affairs, told a congressional committee this week.
"China's land reclamation could potentially have a range of military implications," he said. Beijing could build bases for long-range radar installations, airfields for use by surveillance aircraft and fighters, and harbors for navy and coast guard vessels, he said.
"We're in the process of ensuring that the Chinese have a crystal clear view of what we think of those features," he said.
U.S. warships frequently transit the South China Sea and are often shadowed by Chinese navy vessels, and vice versa.
Navy officials refuse to say how close the Fort Worth, which is designed to operate in shallow water, sailed to the islands claimed by Beijing or the Chinese warships it encountered.
The Fort Worth "encountered multiple [Chinese] warships" and the "interactions" were "professional," the Navy said in a news release. It noted that the ship also "conducted flight operations with its MH-60R Seahawk helicopter."
So far, U.S. and Chinese commanders have been careful not to let their military operations provoke a confrontation. That has not always been the case.
Pentagon officials were furious in August when a Chinese fighter jet did a barrel roll over a Navy P-8 over the South China Sea. The White House condemned the incident as a dangerous provocation.
In 2001, a Chinese fighter jet collided with a Navy EP-3 surveillance plane, forcing the American aircraft to make an emergency landing on nearby Hainan island in Chinese territory.
The decision to send littoral combat ships to the western Pacific is part of the U.S. military focus on Asia and the Pacific that Obama announced four years ago.
Two ships take turns, steaming from San Diego to Singapore on 16-month deployments. Two more will join the effort in 2016, allowing more patrols in regional hot spots, officials said.
"Routine operations like the one Fort Worth just completed in the South China Sea will be the new normal," said U.S. Navy Capt. Fred Kacher, who commands the squadron that includes the ships.
Lawmakers of both parties, and some allies in the region, have criticized the U.S. response so far as insufficient to rein in China's island-building projects.
"I see no price whatsoever that China is paying for their activities in the South and East China Sea," Sen. Bob Corker, (R-Tenn.), chairman of the Senate Foreign Relations Committee, said at a hearing Wednesday. "I see us actually paying a price in our esteem in the region.
Daniel Russel, assistant secretary of State for East Asia, took issue with Corker's criticism, saying that China's operations had backfired by causing other governments in the region to seek U.S. assistance, to build up their own modest navies and coast guards, and to unite in regional forums in calling for a halt to land reclamation.
"I think unquestionably China is paying a price and it's a growing price for its behavior," Russel said.
The U.S. has long refused to take sides in the territorial disputes. But officials stress that man-made islands do not constitute sovereign territory under international law and therefore cannot be used to assert claims to territorial waters.
Chinese officials have given various explanations for the island-building projects. Some have said the new facilities will be used for disaster relief, environmental protection and scientific research. Other officials have said China's military needs to support radar and intelligence gathering in the region.