One of the mysteries of Iran's nuclear program is the fact that, despite periodic warnings about how close Tehran is to acquiring a nuclear weapons capability, the Iranian nuclear program is proceeding at a slower speed than that of earlier nuclear weapons states. Whereas Pakistan and North Korea needed only some 10 years to develop atomic bombs, Iran has had a nuclear program for almost three decades without producing a weapon.
Various explanations could explain this deliberate pace. Iranian leaders might still be debating their nuclear weapons options and not yet committed to pursuing a nuclear weapon or capability. Iran's nuclear activities have also been suffering from design-related technical problems, increasingly tough international sanctions and deliberate foreign sabotage. These factors have combined to impede Iranian efforts to acquire the technologies, equipment and other materials needed to enrich uranium for a possible bomb.
The International Institute for Strategic Studies (IISS) believes that the Iranian government is deliberately moving slowly in order to avoid alarming the international community even further about its intentions, which could galvanize stronger sanctions or even a military response.