"Conducting military exercises over disputed territory in the South China Sea is counterproductive to efforts at easing tensions and maintaining stability," the department said Thursday.
China’s actions "will further destabilize the situation in the South China Sea," it said, adding that the exercises violate China's commitments under the 2002 Declaration on the Conduct of Parties in the South China Sea to avoid activities that would complicate or escalate disputes and affect peace and stability.
The Pentagon said the military exercises are the latest in a long string of China's actions "to assert unlawful maritime claims and disadvantage its Southeast Asian neighbors in the South China Sea."
It urged China to reduce its militarization and coercion of its neighbors in the waters.
The Maritime Safety Administration of China's Hainan Province had announced plans to hold military exercises near Vietnam's Paracel Islands from July 1-5.
Vietnam's Foreign Ministry spokeswoman Le Thi Thu Hang said Thursday the country has sent a diplomatic note to protest the illegal exercises, urging non-repetition of the incident.
Hang said the exercises violated Vietnam’s sovereignty, complicating negotiations for a Code of Conduct of Parties in the South China Sea (COC) between China and ASEAN, and affecting peace.
Vietnam calls the waterway the East Sea.
The country has on multiple occasions condemned China’s illegal actions in the waters, claiming full legal basis and historical evidence to affirm its sovereignty over the Spratly and Paracel Islands in accordance with international law. All activities conducted by any party near either island without prior consent from Vietnam hold no value, it has stressed.