The US has threatened further naval incursions into waters claimed by China after its naval manoeuvres near two artificial islands in the South China Sea prompted an angry rebuke from Beijing.
China summoned the US ambassador to Beijing following the incident and accused the US of a “serious provocation” after the guided-missile destroyer the USS Lassen sailed close to a Chinese artificial island.
But US defence secretary Ash Carter warned on Tuesday that naval operations in the area would continue.
“We will fly, sail and operate wherever international law permits,” said Mr Carter, during a congressional hearing in which lawmakers claimed the US risked losing credibility with its allies in the region if it did not respond.
“There have been naval operations in that region in recent days and there will be more in the weeks and months to come,” he said.
The US navy began its mission through waters near the island at about 6.40am local time on Tuesday.
Mr Carter confirmed that the USS Lassen travelled within 12 nautical miles (22.2km) of the disputed Spratly archipelago, which is at the heart of a controversial Chinese island-building campaign that has soured ties between Washington and Beijing.
Chinese officials were not informed of Tuesday’s mission, US officials said.
The direct military challenge to Beijing’s territorial claims prompted a furious reaction in Beijing.
State television reported that the Chinese vice-foreign minister, Zhang Yesui, had branded the move “extremely irresponsible” during a meeting with the US ambassador to China, Max Baucus.
Messages sent on official feeds on the WeChat social network, which has hundreds of millions of users in China, said that the “US military . . . has invaded the South China Sea”.
Addressing journalists in Beijing, Lu Kang, a foreign ministry spokesman, said that China was strongly dissatisfied with the US navy's actions, which he described as a threat to China's sovereignty.
However, he refused to be drawn on whether China would consider a military response. “I will not answer hypothetical questions,” Mr Lu said.
“We hope that the US side will not take actions that will backfire.”
Mr Lu warned that further “provocative actions” might lead to accelerated Chinese construction in the South China Sea: “It would be a pity for us to realise that we have to strengthen and speed up relevant construction activities.”
The Chinese embassy in Washington said the concept of “freedom of navigation” should not be used as an excuse for muscle-flexing and the US should “refrain from saying or doing anything provocative and act responsibly in maintaining regional peace and stability”.
Military build-up
China’s military build-up in the South China Sea - including the construction of a 3km runway capable of supporting fighter jets and transport planes - has become a major source of tension between Beijing and Washington.
China claims most of the South China Sea, one of the world's busiest sea lanes, although Vietnam, Malaysia, Brunei, the Philippines and Taiwan have rival claims.
Beijing says the islands will have mainly civilian uses, as well as undefined defence purposes.
But satellite photographs have shown the construction of three military-length airstrips by China in the Spratlys, including one each on the Mischief and Subi reefs.
Both reefs were submerged at high tide before China began a massive dredging project in 2014.
It now claims a 12 nautical mile territorial limit around the artificial islands, although the UN Convention on the Law of the Sea says that such limits cannot be set around man-made islands built on previously submerged reefs.
US president Barack Obama said he had held “candid discussions” with his Chinese counterpart, Xi Jinping, over the issue during Mr Xi’s recent state visit .
Speaking earlier this month, officials in Beijing had cautioned the US against “provocative” actions in the South China Sea.
“China will never allow any country to violate China’s territorial waters and airspace in the South China Sea,” foreign ministry spokeswoman Hua Chunying said.
In May, a US spy plane flew over the Spratly Islands, prompting warnings from the Chinese navy to leave, while last month, shortly before Mr Xi's visit, China sent ships to within 12 nautical miles of the Aleutian Islands off Alaska, which it said was a routine exercise after drills with Russia.
Maritime law
The Pentagon insisted it was within its rights under maritime law to enter such waters, in a statement that coincided with a visit to Washington by Indonesian president Joko Widodo.
"The United States is conducting routine operations in the South China Sea in accordance with international law," Bill Urban, a US defence department spokesman told reporters.
“US forces operate in the Asia-Pacific region on a daily basis, including in the South China Sea. All operations are conducted in accordance with international law.”
White House officials said Mr Widodo and Mr Obama had also discussed the issue during their meeting in Washington on Monday and claimed Chinese aggression “increased tensions, eroded trust, and threatened to undermine peace, security, and the economic wellbeing of the region”.
Mr Obama is said to have been under particular pressure to tackle the issue ahead of an upcoming meeting of the Association of Southeast Asian Nations (Asean).
However, pressure was also mounting at home.
Arkansas Republican Dan Sullivan said many members of the senate armed services committee had been concerned that US “inaction” in the South China Sea was “undermining US credibility”.
Security experts in Washington described Tuesday’s intervention as a victory for hawks within the administration, who had been pushing hard for a symbolic gesture against Chinese territorial claims.
Guardian service and agencies
