The Chinese military says it has dispatched warships after U.S. Navy vessels sailed near Beijing-claimed islands in the South China Sea.
The Higgins - a guided-missile destroyer - and the Antietam - a guided-missile cruiser - were sent as part of what has been seen as an attempt by Washington to counter efforts by Beijing to limit freedom of navigation in its waters.
Commenting on the move, which Beijing slammed as a "provocation" and a violation of China's sovereignty, the Chinese Defense Ministry said it was determined to strengthen its combat readiness, increase defense levels, and ensure regional stability.
"Chinese military took immediate actions by dispatching naval ships and aircrafts to conduct legal identification and verification of the United States warships and warn them off", Wu Qian, defense ministry spokesman, said.
"China will continue to take all necessary measures to defend the country's sovereignty and security", the Chinese Ministry of Foreign Affairs noted in another statement.
China claims that all its military forces in the South China Sea are purely defensive.
China now asserts its right to the islands.
Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have conflicting claims in the area.
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China has always been accused of building artificial land masses in that region, which is also claimed by the Philippines, Taiwan, Vietnam and Malaysia, and placing military assets there.
Critics of the operations, known as a "freedom of navigation", have said that they have little impact on Chinese behaviour and are largely symbolic.
Pentagon officials have long complained that China has not been candid enough about its rapid military build-up and using South China Sea islands to gather intelligence in the region. RIMPAC is the world's largest maritime military exercise and is held bi-annually in Hawaii, usually in June and July.
Last week, Chinese bombers landed on islands and reefs claimed by the Philippines, prompting Manila to take "appropriate diplomatic action" on the matter.
'China's continued militarization of disputed features in the South China Sea only serves to raise tensions and destabilize the region, ' Pentagon spokesman Lieutenant Colonel Chris Logan said.
Another unacceptable action would be Chinese construction activities on a disputed shoal in the South China Sea, according to the Philippine diplomat.
President Donald Trump said Wednesday that he was not satisfied with talks aimed at averting a trade war with China.