We are now at the front-end of what is likely to be a contentious debate in the United States over replacing existing nuclear warheads with simpler designs that may never need to be tested. Advocates of the reliable replacement warhead (RRW) programme worry that nuclear deterrence is too important to rest in an aging, cold war arsenal. The RRW programme matters greatly to the US nuclear laboratories because it will give them a renewed sense of purpose and an opportunity to train a new generation of bomb-makers. Critics of the RRW initiative believe strongly that the US needs to dramatically reduce reliance in nuclear weapons and replacing old designs with new ones would invite new proliferation problems. We cannot sidestep this debate by arguing that whatever the US decides will have no bearing on others. As a world leader, US nuclear choices obviously matter. Some countries that have the Bomb will follow the US lead, while others seeking the Bomb will try to deflect international pressures by charging Washington with hypocrisy. At a time when global concerns over proliferation are growing, the United States remains the most important guardian of the global non-proliferation system. So Washington’s decisions on the RRW programme can either accentuate negative nuclear trend lines, or help reverse them. Before the reflexive responses of “hell, no” and “absolutely, yes” to the RRW programme become locked in, it’s at least worth trying to consider outcomes that help US national security without harming the global non-proliferation system. Since US national security depends on strengthening global norms against proliferation, we risk harming both core objectives if we pit one core objective against the other. The narrower our focus, the more we invite either/or choices. The Bush administration’s first cut at the RRW issue is regrettably narrow. Internal deliberations have focused on how best to replace some unspecified portion of our aging nuclear warheads with designs that will be more reliable, easier to maintain, and far less likely to require a resumption of underground nuclear testing.By framing deliberations in this narrow way, the administration has arrived at the conclusion that reliable replacement warheads are needed, and that the Congress should begin this process with initial funding for a RRW version of the W-76 warhead. The W-76, which is approximately seven times more powerful than the weapon that destroyed Hiroshima, is launched from Trident submarines. During the cold war, warheads with 100-kiloton yields were consistent with targeting plans against war-supporting industry, harbours, and mobile missile launchers. The Bush administration implicitly acknowledges that this extensive and expensive swap of old warheads for newer, more reliable designs would be harmful to US global non-proliferation objectives. It therefore seeks to soften the adverse consequences of its preferred course of action by clarifying up-front that the swap would be accompanied by unspecified reductions in the US nuclear stockpile and in deployed nuclear forces. Moreover, the administration emphasises that the new designs should not need to be tested, and that there would be no new roles or missions for the replacement warheads. These statements are unlikely to be reassuring to America’s friends and allies that seek to shore up the troubled international system to prevent proliferation. Most of the globe will view the RRW initiative as contrary to US commitments under the Non-proliferation Treaty because foreign capitals will not be looking at the RRW programme in isolation. Instead, outsiders will view this initiative in the context of the Bush administration’s adamant refusal to join 138 other nations that have ratified a treaty banning nuclear tests, its resistance to a new treaty formalising deeper cuts with Moscow, and its apparent willingness to allow intrusive verification measures governing deep, bilateral cuts to lapse when the Strategic Arms Reduction Treaty expires in 2009.The Bush administration will be leading with its chin on the RRW programme as long as its focus is narrowly confined to how to replace old warheads with new ones. Nuclear-weapon states under the NPT have every right to modernise their stockpiles, but the well-being of the global non-proliferation system mandates that such steps take place in a broader context in which obligations to nuclear disarmament are taken seriously and non-proliferation norms are strengthened.It makes no sense to argue that treaties can be discarded because they are relics of the cold war, but that cold war-era nuclear warheads need to be replaced. Treaties are the backbone of global norms and international efforts to stop and reverse proliferation. Advocates of the RRW programme shoot themselves in the foot and invite blocking action when they oppose or devalue treaties that are central to global non-proliferation system. This bifurcated approach will put an intense spotlight on a high-profile, expensive warhead replacement programme that will proceed in tandem with current warhead refurbishment efforts undertaken by US nuclear laboratories. The world’s most powerful country will thereby clarify the value it places on nuclear deterrence, while simultaneously seeking international support to convince or coerce other countries not to rely on nuclear deterrence. A more holistic approach is needed in order for US national security to be advanced and not negated by nuclear weapons. Rationales for reliable replacement warheads are unlikely to be plausible if they rest on requirements to execute war plans reminiscent of the cold war. Nor are nuclear weapons likely to be helpful in prosecuting the “war on terror”. What actual purposes, beyond generalised notions of deterrence, would RRW serve? If a broader inquiry into the future role of nuclear weapons suggests that they have very narrow utility for the US, and far greater utility for weaker nations, then the scope of an RRW programme could contract and the design of replacement warheads could become very rudimentary, while accompanying diplomatic and treaty initiatives could become far more ambitious.Reliable replacement warhead programmes make sense only if they are one piece on a larger chessboard in which the US reaffirms the global non-proliferation system and demonstrates its core NPT commitment to help create conditions for a world without nuclear weapons. A big picture view of the RRW programme is needed — not one confined to the Pentagon and Department of Energy. By taking a broader view, we might just be able to strengthen national security as well as the global nonproliferation system. Michael Krepon is the co-founder of the Henry L Stimson Centre. This essay is a slightly modified version of an article which appeared in DefenseNews