"act of rebellion against the Crown" in the United Kingdom, and Wilson promised that the illegal action would be short-lived. However, given its self-governing status Rhodesia had no longer been within the United Kingdom's direct sphere of influence for some time, and the facade of continued British rule was rendered a constitutional fiction by UDI. In light of these circumstances, Wilson quickly realised his ability to assert direct leverage over the incumbent Rhodesian government was limited. On 12 October 1965, the United Nations General Assembly had noted the repeated threats of the Rhodesian authorities "to declare unilaterally the independence of Southern Rhodesia, in order to perpetuate minority rule", and called upon Wilson to use all means at his disposal (including military force) to prevent the Rhodesian Front from asserting independence. After UDI was proclaimed, UN officials branded the Rhodesian government as an "illegal racist minority regime" and called on member states to voluntarily sever economic ties with Rhodesia, recommending sanctions on petroleum products and military hardware. In December 1966, the UN further iterated that these sanctions were mandatory, and member states were explicitly barred from purchasing Rhodesian export goods, namely tobacco, chromium, copper, asbestos, sugar, and beef. The British government, having already adopted extensive sanctions of its own, dispatched a Royal Navy squadron to monitor oil deliveries in the port of Beira in Mozambique, from which a strategic pipeline ran to Umtali in Rhodesia. The warships were to deter "by force, if necessary, vessels reasonably believed to be carrying oil destined for (Southern) Rhodesia". Some Western nations, such as Switzerland, and West Germany, which were not UN member states, continued to conduct business openly with Rhodesia – the latter remained the Smith government's largest trading partner in Western Europe until 1973, when it was admitted to the UN. Japan remained the chief recipient of Rhodesian exports outside the African continent, and Iran also supplied oil to Rhodesia in violation of the embargo. Portugal served as a conduit for Rhodesian goods, which it exported through Mozambique with false certificates of origin. South Africa, too, refused to observe the UN sanctions. In 1971, the Byrd Amendment was passed in the United States, permitting American firms to go on importing Rhodesian chromium and nickel products as normal. Despite the poor showing of sanctions, Rhodesia found it nearly impossible to obtain diplomatic recognition abroad. In 1970, the United States declared it would not recognise