In 1964, all eyes were on a nuclear China and India
The intelligence community viewed China's first nuclear test in 1964 as a potential catalyst for regional arming but was unsure of Israel's nuclear intent at the time, according to a recently declassified national intelligence estimate.
The 1964 NIE report (.pdf) posted by the National Security Archive and the Nuclear Proliferation International History Project, declassified in its entirety by the CIA, provides insight into expected nuclear capabilities and intents of other countries on Oct. 21, 1964.
The intelligence community at the time was most interested in China, India, Israel, and Sweden. China's nuclear test on Oct. 16, 1964 raised tensions with India because it had lost territory along its Himalayan border to China in the 1962 Sino-Indian War.
This led report authors to believe that "chances are better than even that India will decide to build nuclear weapons within the next few years." While India could produce plutonium, it did not conduct its first nuclear test until May 18, 1974 when it detonated a nuclear device called the Peaceful Nuclear Explosive.
The report also estimates that Israel had not yet committed itself to a nuclear weapons program but that the armament of neighbor states could lead to this if it could not acquire a sufficient amount of conventional weapons. The National Security Archive says this surprisingly contradicts a 1963 NIE (.pdf) that said "the Israelis, unless deterred by outside pressure, will attempt to produce a nuclear weapon."
For other nations, the reports said there was a less than even chance Sweden would shift its peaceful program to one making nuclear weapons and that it expected West Germany and Italy to avoid weaponizing their technology despite nuclear power investments. It also said Japan did not possess enough uranium and could not secure a weapons-grade supply.
The report views safety issues around nuclear devices as somewhat of a boon, since they can serve as a deterrent for some countries to pursue weapons. Even if weapons do spread, the report fits with modern convention saying "the very presence of nuclear weapons might even bring a new sense of prudence" for conflicts or aggressions involving nuclear-capable countries or their allies and neighbors.
- read the declassified report via George Washington University's National Security Archive