The U.S. Navy on Saturday sent a warship on a “freedom of navigation operation” (FONOP) near disputed islands in the South China Sea for the second time in less than a week.

The Navy said it had sent the USS Benfold guided-missile destroyer near the contested Spratly Islands, days after China claimed to have expelled the same vessel from waters near the disputed Paracel chain of islets further north in the strategic waterway, the latest instance of tension between the two nations’ armed forces.

The U.S. Navy said the operation was conducted to uphold international law by challenging the restrictions on “innocent passage” it says are imposed by China, Taiwan and Vietnam, which in addition to Malaysia, Brunei and the Philippines each claim sovereignty over some or all of the Spratly chain.