WASHINGTON, -- An American B-52 bomber on a routine mission over the South China Sea unintentionally flew within two nautical miles of an artificial island built by China, senior defense officials said, exacerbating a hotly divisive issue for Washington and Beijing.
Pentagon officials told The Wall Street Journal they are investigating why one of two B-52s on the mission last week flew closer than planned to Cuarteron Reef in the Spratly Islands, an area where China and its neighbors have competing territorial claims. A senior U.S. defense official said that bad weather had contributed to the pilot flying off course and into the area claimed by China.
Beijing filed a formal diplomatic complaint with the U.S. Embassy in Beijing, which prompted the Pentagon to look into the matter.
The flight comes amid rising tensions over China’s island-building program and U.S. operations to challenge Beijing’s broad but vaguely defined claims in the area.
In late October, a U.S. Navy destroyer sailed within 12 nautical miles of another Chinese-built island in the Spratlys. Two American B-52s also flew close to the islands last month but didn’t go within 12 nautical miles, a boundary marking a country’s territorial waters.
Unlike those patrols, the route taken by the B-52 this week wasn’t planned, according to the Pentagon. “For this mission, there was no intention of flying to within 12 nautical miles,” said Cmdr. Bill Urban, a Pentagon spokesman.
“The Chinese have raised concerns with us about the flight path of a recent mission,” he said. “We are looking into the matter.”
China’s Defense Ministry said that both of the American B-52 bombers on Dec. 10 “entered without authorization the airspace around the relevant islands and reefs” of the Spratlys, but didn’t specify the precise area.
The ministry said this and other U.S. operations in the area were “serious military provocations” that endangered Chinese personnel and could cause the militarization of the South China Sea. It added that the Chinese military would take “all necessary measures” to protect China’s sovereignty.
The incident is diplomatically awkward for the White House, which is trying to maintain stable ties with the world’s No. 2 economy while responding to pressure from U.S. allies in Asia, as well as the Pentagon and Congress, to push back against Beijing’s recent military assertiveness.
Aside from the South China Sea, other security issues roiling relations included alleged cyberattacks by China on the U.S.
On Wednesday, Beijing lodged another formal protest after the U.S. approved a $1.83 billion arms sale to Taiwan, an island that China claims but doesn’t control.
Cuarteron lies about 1,000 kilometers (620 miles) south of China’s Hainan island. Since mid-2014, reclamation has expanded the reef by more than 230,000 square meters (57 acres); it now includes two helipads, possible gun or missile emplacements and two possible radar towers, according to the Center for Strategic and International Studies in Washington.
Washington has grown alarmed at the speed at which China’s artificial islands have expanded—from a total of 2,000 acres earlier this year to more than 3,000 acres by September, according to Defense Department documents.
Cuarteron is one of seven rocks and reefs in the Spratlys where China has built artificial islands in the past year, as part of what neighbors fear is a program to better enforce its claims and establish control over one of the world’s busiest shipping routes.
China says it guarantees freedom of navigation, but has “indisputable” sovereignty over all South China Sea islands and adjacent waters. It says the new facilities are for civilian purposes such as weather monitoring, as well as national defense.
Many maritime law experts categorize Cuarteron as a rock rather than a reef, a difference that some maritime experts say figures into Washington’s strategy in the South China Sea.
Under the United Nations Convention on the Law of the Sea, natural islands and rocks are entitled to territorial seas stretching out 12 nautical miles, whereas most reefs that are submerged at high tide aren’t.
Thus, some maritime experts say Washington had planned to focus its overflights and ship passages on Chinese installations built on such reefs.
Cmdr. Urban said the Pentagon didn’t consider this week’s B-52 flight to be a freedom of navigation operation. The term is used by the Pentagon to describe missions meant to challenge what the U.S. sees as excessive claims to territorial waters.
Cmdr. Urban said Chinese personnel on the ground warned the aircraft during the flight but there was no indication that the Chinese military had scrambled jet fighters. He declined to say whether any disciplinary action had been taken or if other flights had been grounded.
While the U.S. says it doesn’t take sides in the territorial dispute, U.S. officials, including Defense Secretary Ash Carter, have said the U.S. will fly or sail wherever it believes international law permits.
The U.S. conducts routine B-52 flights from Andersen Air Force Base in Guam throughout the Asia-Pacific region under a program known as “continuous bomber presence” started in 2004 to demonstrate the U.S. commitment to security in the region.
The U.S. Air Force B-52 strategic bomber midair refueling.