Nine months before China's first nuclear test in 1964, then-Prime Minister Hayato Ikeda believed it would be years before China developed nuclear weapons, declassified diplomatic documents showed Thursday.

Beijing "still has a long way (to go) to make nuclear weapons," Ikeda (1899-1965) is quoted as telling U.S. Secretary of State Dean Rusk during talks in his office on Jan. 28, 1964, according to a document dated the same day.

In reply, Rusk (1909-1994) said the United States would not be surprised if China detonated a nuclear device in one to two years, the top-secret document said.

China conducted its first nuclear test on Oct. 16, 1964, and detonated a nuclear bomb the following year.

A day after the first test, China's then-Premier Zhou Enlai (1898-1976) said in a letter to Ikeda that China was forced to develop nuclear arms for its own defense as the Cold War intensified but promised not to engage in first use, a translation of the letter showed.

In the meeting with Rusk, Ikeda said China's detonation of one or two nuclear devices would be less cause for concern than the threat posed by the Soviet Union, which was believed to have deployed nuclear arms to nearby Sakhalin and the Kuril Islands.

Ikeda, who was in power between 1960 and 1964, also said that China would be capable of testing a nuclear device in the future but that it would be long time before it developed an actual nuclear weapon, the documents said.

Rusk was U.S. secretary of state between 1961 and 1969 under presidents John F. Kennedy and Lyndon Johnson.