WASHINGTON—The Pentagon conducted a Navy patrol in the South China Sea, U.S. officials said Wednesday, the first such operation under President Donald Trump designed to send a signal to China about U.S. intentions to keep critical sea lanes open in the Pacific Ocean.

The patrol, known as a freedom of navigation operation, was conducted Wednesday around Mischief Reef, one of a chain of disputed islands in the South China Sea. The guided-missile destroyer USS Dewey conducted the patrol, according to U.S. officials.

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