A/RES/55/33 3. Urges the nuclear-weapon States to stop immediately the qualitative improvement, development, production and stockpiling of nuclear warheads and their delivery systems; 4. Also urges the nuclear-weapon States, as an interim measure, to de-alert and deactivate immediately their nuclear weapons and to take other concrete measures to reduce further the operational status of their nuclear weapon systems; 5. Reiterates its call upon the nuclear-weapon States to undertake the stepby-step reduction of the nuclear threat and to carry out effective nuclear disarmament measures with a view to the total elimination of these weapons; 6. Calls upon the nuclear-weapon States, pending the achievement of the total elimination of nuclear weapons, to agree on an internationally and legally binding instrument on the joint undertaking not to be the first to use nuclear weapons, and calls upon all States to conclude an internationally and legally binding instrument on security assurances of non-use and non-threat of use of nuclear weapons against non-nuclear-weapon States; 7. Urges the nuclear-weapon States to commence plurilateral negotiations among themselves at an appropriate stage on further deep reductions of nuclear weapons as an effective measure of nuclear disarmament; 8. Underlines the importance of applying the principle of irreversibility to the process of nuclear disarmament, nuclear and other related arms control and reduction measures; 9. Welcomes the positive outcome of the 2000 Review Conference of the s Parties to the Treaty on the Non-Proliferation of Nuclear Weapons and the unequivocal undertaking by the nuclear-weapon States, in the Final Document of the Review Conference, to accomplish the total elimination of their nuclear arsenals leading to nuclear disarmament, to which all States parties are committed under article VI of the Treaty, 8 and the reaffirmation by the States parties that the total elimination of nuclear weapons is the only absolute guarantee against the use or threat of use of nuclear weapons,13 and calls for the full and effective implementation of the steps set out in the Final Document; 10. Calls for the immediate commencement of negotiations in the Conference on Disarmament, on a non-discriminatory, multilateral and internationally and effectively verifiable treaty banning the production of fissile material for nuclear weapons or other nuclear explosive devices on the basis of the report of the Special Coordinator11 and the mandate contained therein; 11. Urges the Conference on Disarmament to agree on a programme of work which includes the immediate commencement of negotiations on such a treaty with a view to their conclusion within five years; 12. Calls for the conclusion of an international legal instrument or instruments on adequate security assurances to non-nuclear-weapon States; 13. Calls also for the early entry into force and strict observance of the Comprehensive Nuclear-Test-Ban Treaty;10 14. Expresses its regret that the Conference on Disarmament was unable to establish an ad hoc committee on nuclear disarmament at its 2000 session, as called for in General Assembly resolution 54/54 P; 34