The conclusion of a comprehensive nuclear test ban is of critical importance for the future of arms limitation and disarmament. As the 1980 report of the Secretary-General concluded, a comprehensive nuclear test ban is regarded as the first and most urgent step towards the cessation of the nuclear arms race and, in particular, of its qualitative aspects. It could serve as an important measure for the non-proliferation of nuclear weapons, both vertical and horizontal. It would have a major arms limitation impact in that it would make it difficult, if not impossible, to develop new designs of nuclear weapons and would also place constraints on the modification of existing weapon designs. The permanent cessation of all nuclear-weapon tests has long been sought by the world community and its achievement would be an event of great international significance.