The USS Hopper carried out an "innocent passage" within 12 miles of Scarborough Shoal on Wednesday evening, said a U.S. official. The guided missile destroyer was shadowed during the operation by a Chinese Navy ship.
The U.S. official described the Hopper’s patrol as an "innocent passage" and not a freedom of navigation operation (FONOP) under the strict legal definition, but "the message was the same."
Under international law a nation's territorial waters extend 12 miles from its shoreline.
China's Foreign Ministry said in a statement that the Hopper had sailed within its 12 mile territorial limit "without gaining permission from the Chinese government."
"What the U.S. vessel did violated China's sovereignty and security interests, put the safety of Chinese vessels and personnel who were in the relevant waters for official duties under grave threat, and contravened the basic norms for international relations," the statement added.
"China is strongly dissatisfied with that and will take necessary measures to firmly safeguard its sovereignty," said the statement.
The U.S. Navy has previously conducted FONOPs in the South China Sea through other disputed island chains claimed by China, including the Spratleys and the Paracels. Pentagon officials stress that FONOPs are conducted worldwide and are intended to demonstrate freedom of navigation through international waters.
"The United States conducts routine and regular FONOPs, as we have done in the past and will continue to do so in the future," said Lt. Commander Nicole Schwegman, a spokeswoman for the U.S. Navy's Pacific Fleet.
"We have a comprehensive FONOP program under which U.S. forces challenge excessive maritime claims across the globe to demonstrate our commitment to uphold the rights, freedoms and lawful uses of the sea and airspace guaranteed to all nations under international law. FONOPs are not about any one country, nor are they about making political statements. FONOPS are designed to comply with international law and not threaten the lawful security interest of coastal States."