Between the poles of nuclear-weapons acquisition and transparent disarmament lies a third option: cultivating ambiguity about capabilities. The current crises with Iran and North Korea are playing out against the backdrop of the contrasting nonproliferation precedents set in 2003 - in Iraq, through a change of regime, and, in Libya, through change within a regime. Washington has sent mixed messages to Tehran and Pyongyang whether the US objective is regime change or behaviour change. Coercive diplomacy, combining credible inducements and penalties to roll back their nuclear programmes, is not possible when the goal is the maximalist one of regime change. But even if the United States clarifies its objective, negotiations with North Korea and Iran can realistically aim only to narrow, but not to eliminate, the ambiguity. A strategy of containment, whose key elements are deterrence and reassurance, offers the best approach for narrowing and hedging against these states' nuclear ambiguity.