<P> After Cuba shot down two unarmed Brothers to the Rescue planes in 1996, killing three Americans and a U.S. resident, a bi-partisan coalition in the United States Congress approved the Helms - Burton Act . The Title III of this law also states that any non-U.S. company that "knowingly trafficks in property in Cuba confiscated without compensation from a U.S. person" can be subjected to litigation and that company's leadership can be barred from entry into the United States . Sanctions may also be applied to non-U.S. companies trading with Cuba . This restriction also applies to maritime shipping, as ships docking at Cuban ports are not allowed to dock at U.S. ports for six months . It's important to note that this title includes waiver authority, so that the President might suspend its application . This waiver must be renewed every six months and traditionally it has been . </P> <P> In response to pressure from some American farmers and agribusiness, the embargo was relaxed by the Trade Sanctions Reform and Export Enhancement Act, which was passed by the Congress in October 2000 and signed by President Bill Clinton . The relaxation allowed the sale of agricultural goods and medicine to Cuba for humanitarian reasons . Although Cuba initially declined to engage in such trade (having even refused U.S. food aid in the past, seeing it as a half - measure serving U.S. interests), the Cuban government began to allow the purchase of food from the U.S. as a result of Hurricane Michelle in November 2001 . These purchases have grown since then, even though all sales are made in cash . In 2007, the U.S. was the largest food supplier of Cuba, which nevertheless is largely self - sufficient, and its fifth largest trading partner . </P> <P> In some tourist spots across the island, American brands such as Coca - Cola can be purchased . Ford tankers refuel planes in airports and some computers use Microsoft software . The origin of the financing behind such goods is not always clear . The goods often come from third parties based in countries outside the U.S., even if the product being dealt originally has U.S. shareholders or investors . This can be seen, for example, with Nestlé products (which have a 10% US ownership) that can be bought in Cuba with Cuban convertible pesos (CUCs). These CUC pesos are hard currency that are traded in foreign exchange against the US dollar, Euro and other currencies . </P> <P> In November 1991, the Cuban ambassador, Ricardo Alarcon, in a speech to the UN General Assembly, cited 27 recent cases of trade contracts interrupted by US pressure . The British journal Cuba Business claimed that British Petroleum was seemingly dissuaded by US authorities from investing in offshore oil exploration in Cuba despite being initially keenly interested . The Petroleum economist claimed, in September 1992, that the US State Department vigorously discouraged firms like Royal Dutch Shell and Clyde Petroleum from investing in Cuba . This pressure did not work in all cases . According to the Mexican Newspaper El Financiero, the US ambassador to Mexico, John Negroponte travelled to meet two Mexican business men who had signed a textile deal with Cuba on October 17, 1992 . Despite the representation, the deal went ahead and was eventually worth $500 million in foreign capital . All of this happened before the signing of the Cuban Democracy Act . </P>

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