The UN General Assembly and Security Council quickly joined the UK in condemning UDI as illegal and racist. Security Council Resolutions 216 and 217, adopted in the days following Smith's declaration, denounced UDI as an illegitimate "usurpation of power by a racist settler minority", and called on nations not to entertain diplomatic or economic relations. No country recognised Rhodesia as independent. Black nationalists in Rhodesia and their overseas backers, prominently the Organisation of African Unity (OAU), clamoured for the UK to remove Smith's government with a military invasion, but Britain dismissed this option, citing logistical issues, the risk of provoking a pre-emptive Rhodesian strike on Zambia, and the psychological issues likely to accompany any confrontation between British and Rhodesian troops. Wilson instead resolved to end UDI through economic sanctions, banning the supply of oil to Rhodesia and the import of most Rhodesian goods to Britain. When Smith continued to receive oil through South Africa and Portuguese Mozambique, Wilson posted a Royal Navy squadron to the Mozambique Channel in March 1966. This blockade, the Beira Patrol, was endorsed by UN Security Council Resolution 221 the following month.