Beijing summoned the US ambassador to China to express its "strong discontent" after a US naval destroyer sailed close to islets occupied by China but claimed by the Philippines, state media reported.
Beijing said the USS Lassen illegally entered Chinese territorial waters when it sailed early Tuesday near the disputed Spratly, or Nansha, group of islands.
"China will do whatever necessary to oppose deliberate provocation from any country," Deputy Foreign Minister Zhang Yesui was quoted as saying by the Xinhua news agency late Tuesday, after summoning US Ambassador Max Baucus.
Zhang dismissed US concerns that China's territorial claims in the region were a threat to transport or regional security. (dpa)