The officer in charge of the US Indo-Pacific Command says the security situation in the region and beyond is experiencing potentially the most dangerous period since World War Two.
Admiral John Aquilino made the remark in a speech at the Shangri-La Dialogue, an Asian security forum meeting in Singapore, on Saturday.
The meeting has been underway since Friday with defense ministers and other government officials from Asian and Western countries taking part.
During Saturday's speech, Admiral Aquilino pointed out that China has been taking destabilizing actions throughout the Indo-Pacific, including coercion and unsafe intercepts against the US allies and partners.
He also noted that North Korea's nuclear and missile tests continue to destabilize the region and threaten the livelihood of all nations.
With China in mind, the admiral indicated the need of "a resolve to prevent conflict through maintaining open lines of communication to ensure that competition does not escalate into crisis".
China's Defense Minister Wei Fenghe is scheduled to deliver a speech on Sunday, the last day of the meeting.