In an unusually strong statement by the Pentagon, the U.S. has accused Beijing of employing "bullying tactics" in the disputed South China Sea, citing what it said was "coercive interference" in oil and gas activities in waters claimed by Vietnam.

"China will not win the trust of its neighbors nor the respect of the international community by maintaining its bullying tactics," the U.S. Defense Department said in a statement released Monday.

It said Beijing's actions "to coerce ASEAN claimants, station offensive military systems, and enforce an unlawful maritime claim raise serious doubts over China's credibility," adding that the U.S. would continue to support its allies and partners "to ensure freedom of navigation and economic opportunity throughout the entire Indo-Pacific."