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

A secret report addressed to Minister of Foreign Affairs Mario Gibson Barbosa by Amb. Paulo Nogueira Batista (Brazilian Embassy, Bonn) describing alternatives for the establishment of comprehensive, long-term nuclear agreements between Brazil and a “country to be defined.” The report suggests that given the trends in uranium production in the US and Europe, Brazil needed to either associate itself with France to purchase gas diffusion technology or develop, together with Germany, ultracentrifugation or jet nozzle technologies. The notion was that “countries that decide to develop their own enrichment capacity will not only occupy a privileged competitive position but also will become part of an oligopoly with obvious political implications.” Nogueira Batista was worried, however, that Germany might not be able to offer Brazil centrifugation technology under existing obligations.