On the eve of a United Nations vote on a proposed ban on human cloning, a group of leading stem cell scientists made a final appeal to the UN General Assembly on 5 November not to outlaw human therapeutic cloning. A total ban on both human reproductive cloning and therapeutic cloning has been proposed by Costa Rica, and is supported by the United States. The human cloning policy institute (HCPI), however, has mobilised some of the world's leading scientists in support of a Belgian compromise convention, which encourages member states to ban reproductive cloning, but not somatic cell nuclear transfer (therapeutic cloning). HCPI Director Bernard Siegel argues that: 'It is extremely important to recognise the difference between reproductive and therapeutic cloning. Informed scientific opinion worldwide supports therapeutic cloning of stem cells.' Mr Siegel said that failure to pursue therapeutic cloning techniques would be 'equivalent to turning our backs on one of the greatest potential medical advances of our time and would thereby destroy the hope for understanding and treatment of many deadly diseases and conditions.' Among the supporters of HCPI's position is Dr Ian Wilmut, the Roslin Institute scientist who cloned Dolly the sheep, and the retired World Court judge from Sri Lanka, Christopher Weeramantry. The HCPI is keen to express its opposition to reproductive human cloning, and lends support to a World Court initiative that seeks to declare the practice a crime against humanity. 'A declaration that human reproductive cloning is a crime against humanity will prompt all member states to crack down on those activities [and] serve as a lasting deterrent,' Mr Siegel concluded.