HONG KONG — Jeremy Hunt, the new British foreign secretary, made a diplomatic gaffe on Monday, calling his Chinese-born wife Japanese during a discussion with his counterpart in Beijing.

China and Japan have been longtime military rivals: During the 1930s and 1940s, Japan invaded and seized much of China, provoking a conflict that still haunts the nation.

Mr. Hunt committed the flub during a meeting with China’s foreign minister, Wang Yi.

“My wife is Japanese — my wife is Chinese,” he said. “That’s a terrible mistake to make.”