The failure of last weeks United Nations summit to deliver an agreement designed to prevent terrorists acquiring weapons of mass destruction was sabotaged by the US, senior diplomats have told The Observer. Officials involved in the negotiations have confirmed that the Bush administrations refusal to countenance any form of disarmament blocked attempts to push measures that would prevent regimes seeking to develop a nuclear capability. It contradicts reports last week that the US had in fact been furious that plans to crack down on nuclear proliferation were stripped out of the final UN document. However, diplomats speaking on condition of anonymity have revealed it was in fact President Bush who scuppered what the UN believed was a crucial move in helping make the world safer from the risk of terrorists obtaining a nuclear threat. Sources reveal that the move has heightened further tensions between the Americans and furious UN officials who believe the issue remains the greatest threat to world peace. Kofi Annan, secretary-general of the UN, told world leaders that the decision to drop all references in the final UN text to disarmament was inexcusableو saying that weapons of mass destruction pose a grave danger to us all. One diplomat said the US refused to accept the logical premise that it must engage in disarmament if it does not to want to encourage a new nuclear arms race.