The United States flew two B-52 bombers over the weekend near man-made islands constructed by China in the South China Sea, a U.S. official told The Hill, in a clear challenge to China’s territorial claims to the area.
The bombers made one pass within 12 nautical miles of the islands, the official said, in what the military refers to as a "freedom of navigation" operation.
The Pentagon released its own account of the flights after The Hill's report was published.
Pentagon spokesman Navy Cmdr. Bill Urban said two B-52s took off and returned to Guam on Nov. 8 and 9 respectively, flying a "routine mission in international airspace in the vicinity of the Spratly Island of the Spratly Islands in the South China Sea."
Urban confirmed that the pilots received two verbal warnings from a Chinese ground controller "despite never venturing within 15 nautical miles of any feature," he said. "Both aircraft continued their mission without incident, and at all times operated fully in accordance with international law."
The U.S. flights came after China recently placed advanced J-11 fighter aircraft on Woody Island, which is one of five artificially constructed landmasses in the area.
Experts say the deployment of the J-11 jets is a signal that China is prepared to protect its territorial claims to their man-made islands in the Spratly Island archipelago, which is made up hundreds of reefs, islets, atolls, cays and islands. Parts of the archipelago are also claimed by Brunei, Malaysia, the Philippines, Taiwan and Vietnam.
China first began building islands on top of partially submerged reefs about two years ago, but has become increasingly assertive in claiming ownership of the area. Its officials have requested that ships provide prior notification to Chinese authorities when sailing within 12 nautical miles of what it claims is its territory.
The U.S. bomber flights took place after Defense Secretary Ashton Carter visited the region last week, although they were planned long in advance, the U.S. official said.
The flights also took place a little more than a week after the U.S. sent the guided-missile destroyer USS Lassen within 12 nautical miles of Subi Reef, one of China's claimed artificial islands in the South China Sea, on Oct. 27, which prompted outrage from China.
Some experts argue the USS Lassen operation sent mixed messages, since it was conducted in the manner of an "innocent passage" — when a ship takes measures to convey it is innocently passing through waters belonging to another nation — that would tacitly affirm China's claims.
Pentagon officials have pushed back against the notion it was an "innocent passage," though an official confirmed to Reuters that the Lassen turned off its fire control radars while transiting past Subi Reef, avoiding any military operations during that time.
Top U.S. officials were also hesitant to confirm the Lassen's sail-by in public, drawing fierce criticism from members of Congress who argued it made no sense to keep the operation private if it was meant to be a public demonstration against China's claims.
On Monday, Senate Armed Services Committee Chairman John McCainJohn McCainSenate panel votes to confirm Tillerson Overnight Defense: Trump nominates Air Force secretary | Senate clears CIA director | Details on first drone strike under Trump McCain: Trump's withdrawal from TPP a 'serious mistake' MORE (R-Ariz.) sent a letter to Carter urging the Pentagon to "publicly clarify, to the greatest extent possible, the legal intent behind this operation and any future operations of a similar nature."
“Given the sensitive political dynamics and detailed legal implications of our actions, it is vital that there be no misunderstanding about our objectives in either the Asia-Pacific region or within the international community," McCain wrote in the letter, published online by the U.S. Naval Institute.
While the bomber flights are unmistakably a challenge to China's claims, U.S. officials appear to want to keep such operations quiet, perhaps due to political sensitivities with China.
The U.S. wants to maintain a peaceful and productive relationship with China as it "rebalances" to the Asia-Pacific and works on a number of issues ranging from economic cooperation to climate change to cyber security.
At his first stop after leaving the region, Carter spoke openly about the United States' intentions to conduct more freedom of navigation operations, without delving into specifics.
"We will continue to fly, sail and operate wherever international law allows," he said on Saturday in California at the Reagan National Defense Forum. "It's important to remember that America's rebalance and this regional security architecture has never aimed to hold any nation back or push any country down.
"The United States wants every nation to have an opportunity to rise, because it's good for the region and good for all our countries. And that includes China. We welcome its rise, and its inclusion in this architecture; but it must uphold [China's] President Xi [Jinping]'s pledge not to 'pursue militarization' in the South China Sea," he added.
China's increasingly aggressive territorial claims have inflamed critics of President Obama's foreign policy, who say the U.S. is not doing enough to contest them.
While Obama visited Alaska in September, a flotilla of five Chinese ships came within 12 nautical miles of U.S. territorial waters. Pentagon officials called the incident an "innocent passage."
Republican presidential candidate Gov. Chris Christie (R-N.J.) criticized the White House's response to China's maritime territorial claims during this week’s debate.
"I will tell you this, they're building these artificial islands in the South China Sea and the president won't — up until recently, wouldn't sail a ship within 12 miles or fly a plane over it," Christie said.
"I'll tell you this, the first thing I'll do with the Chinese is I'll throw — I'll fly Air Force One over those islands. They'll know we mean business."
— This story was updated at 5:13 p.m.