U.S. media outlets cited an unmanned Pentagon official as saying USS Lassen was patrolling within 12 nautical miles of the Spratly Islands, which Beijing had built over the past year. The U.S. warship has reportedly passed the Subi and Mischief reefs as part of the hours-long patrol, the report says.
"We have been a close exchange of information," Yoshihide Suga said at a daily briefing, declining further "comment on every move" by U.S. forces.
The Chinese Foreign Ministry advised the United States not to act "rashly or make much ado about nothing" in its foray into the South China Sea.
Read alsoNew Chinese fighter jet poised to reach the export marketCountries located in and around the areas of the South China Sea, including the Philippines, Malaysia and Vietnam, have expressed competing claims to the disputed Spratly Islands.
The United States has warned it does not recognize the sovereignty of the Chinese claims and has repeatedly raised concerns over Beijing's activities in the region.
