The request was made by Prime Minister Eisaku Sato on his first visit to the United States in 1965, a year after China's successful atomic test, Kyodo news service reported Monday, quoting diplomatic documents disclosed by the Japanese foreign ministry.
Sato informed U.S. Defense Secretary Robert McNamara in January 1965 that Japan expected the United States to come to its aide in the event of a nuclear attack, and that Washington could use its sea-based nuclear weapons, the Yomiuri Shimbun reported.
The report said the documents confirmed Sato, in his prior summit meeting with U.S. President Lyndon Johnson, had received assurance the United States would protect Japan under its nuclear umbrella.
McNamara was quoted as saying there would be no technical problems arising from Japan's opposition to having its own nuclear weapons if the United States were to fire such weapons from the sea.
The United States, in light of China's nuclear test, also reportedly asked Sato to raise Japan's defense budget in the next decade.
Kyodo reported that Sato said while Japan had the capability to make nuclear weapons, it did not intend to possess or use them. He also had urged the United States to be cautious in remarks about bringing any nuclear arms onto Japanese territory.