NEW YORK — The tacit agreements between Japan and the United States concerning U.S. nuclear-armed vessels visiting Japanese ports were necessary in the 1960s due to the unstable political climate at the time, according to a leading American expert on Japan.

"Probably in that environment any agreement by the Japanese government to allow nuclear weapons to enter ports — any public agreement — would have caused even more demonstrations and uprising," George Packard, president of the U.S.-Japan Foundation, said in a recent interview at his New York office.

Packard has had a wide-ranging career in academia, government service, journalism and as a writer.