BATA, Equatorial Guinea—Classified American intelligence reports suggest China intends to establish its first permanent military presence on the Atlantic Ocean in the tiny Central African country of Equatorial Guinea, according to U.S. officials. The officials declined to describe details of the secret intelligence findings. But they said the reports raise the prospect that Chinese warships would be able to rearm and refit opposite the East Coast of the U.S.—a threat that is setting off alarm bells at the White House and Pentagon. Principal deputy U.S. national security adviser Jon Finer visited Equatorial Guinea in October on a mission to persuade...