Defense Secretary Ashton Carter says China could be erecting “a great wall of self-isolation” with its increasingly provocative moves against its neighbors.

Carter focused on the Asia-Pacific region Friday in his commencement speech at the U.S. Naval Academy.

He says America’s allies and partners are voicing concerns about China’s activity, both publicly and privately, and at the highest levels.

China and Japan both claim uninhabited islands in the South China Sea.

Carter says the United States is committed to upholding core principles including freedom of navigation and commerce and peaceful resolution of disputes. He says China’s actions “challenge fundamental principles, and we can’t look the other way.”

(AP)