The treaty creating the Latin American Nuclear Free Zone (LANFZ) was signed at Tlatelolco, Mexico, on 14 February 1967. Taking a close look at key provisions, INR found that the entry into force provisions included loopholes which “unenthusiastic” states could use so the treaty did not cover their territory.

This lengthy report was State Department Bureau of Intelligence and Research's contribution to the first National Intelligence Estimate on the nuclear proliferation, NIE 100-6-57. Written at a time when the United States, the Soviet Union, and the United Kingdom were the only nuclear weapons states, the “Fourth Country” problem referred to the probability that some unspecified country, whether France or China, was likely to be the next nuclear weapons state. Enclosed with letter from Helmut Sonnenfeldt, Division of Research for USSR and Western Europe, to Roger Mateson, 4 June 1957, Secret

According to the 1985 report, the Argentines “have achieved at least a proof of principle of uranium enrichment via gaseous diffusion.” In other words, they had a workable system. Nevertheless, the enrichment plant would not be “fully operational until 1987-1988.” While the assessment of Argentine interest in nuclear weapons did not change, CIA analysts asserted that “Argentina continues to develop the necessary facilities and capabilities that could support a nuclear weapons development effort.”

The US Embassy in Brazil quotes a Brazilian ministry official who declares Brazil will continue its nuclear program “despite all the threats and reprisals” from the US. The unnamed official goes on to say, “The Americans, our allies, are behaving in a way worse than that of our common enemies, the Russians.”