On 7 December 1941 Japanese aircraft launched an attack on US battleships anchored at Pearl Harbor, resulting the next day in a declaration of war by the US against Japan. Three days later Germany declared war on the US. With the US a fully fledged belligerent in a global conflict, a new type of partnership between the US and Britain, unprecedented in the history of Anglo-American relations, ensued. Throughout 1942 the unity of purpose between the two countries was accentuated by the perilous military threats faced by the Allies. Despite South America's geographic isolation from the European and Asian theatres of conflict, one effect of the new accord between the two countries was moves towards cooperation and collaboration in commercial matters between the US and Britain in the region. This cooperation came in the form of aligning the two countries' blacklisting policies in South America, and collaborating in the supply of essential goods.

However, cooperation between the US and Britain in the commercial affairs of South America was continually hampered throughout the first half of 1942 by conflicting trends on both sides of the Atlantic. For Britain the new co-belligerent status of the two countries removed the impetus to placate US criticisms of British trade practices that had actuated British policy during the period of US neutrality. In its place British officials sought to forge a partnership with the US which would entail an active role for Britain in directing the economic affairs of Latin America.