The United States and Portugal traditionally considered each other friends and allies. These sentiments were reinforced by the large number of Portuguese immigrants to the United States and the growing economic and political importance of this Portuguese community. Since 1943, when the United States built the Lajes Air Base on Terceira Island in the Azores, American interests in Portugal were mainly strategic and military. In return for the use of this vitally important base, the United States gave military aid to Portugal. Portugal also benefited from the European Recovery Program (ERP), more commonly known as the Marshall Plan. During the 1960s and early 1970s, relations between the two countries were sometimes strained because the United States took an anticolonial stand with regard to Portuguese Africa.

United States officials were not worried initially by the Revolution of 1974. They assumed that General Spínola, a military man and a conservative, would maintain control. As the revolution moved sharply to the left, however, and it appeared possible the PCP might come to power, United States officials became uneasy. Frank Carlucci, the United States ambassador in Lisbon, directed a campaign to aid democratic groups. The United States and its NATO allies provided assistance to the socialists and socialist trade unions because they were viewed as the best alternative to a communist takeover. The United States also sought to rally the moderate elements within the military and in Portugal generally. The campaign paid off as Portugal remained democratic.

United States assistance, presence, and involvement remained high during the late 1970s. But as Portuguese politics came to resemble those of other West European nations during the 1980s, United States assistance declined. In 1983 the base agreement was renegotiated, but Portuguese officials were subsequently disappointed by a reduction in American military aid. As part of the base agreement, the Luso-American Development Foundation was created to promote economic and cultural ties between the two countries. The next base negotiations, scheduled for the early 1990s, were certain to be onerous as the two countries each sought to realize their respective aims. The United States would continue to have a keen interest in the Lajes Air Base, the only such base available, while Portugal, less dependent on the United States as it became integrated into Europe, would have a strong hand at the negotiating table.

Data as of January 1993