The Islamic Republic is immersed in an intense debate regarding the direction of its nuclear programme. What Iran will do is likely to depend on the type of relationship it has with the United States, the emerging security architecture in the Persian Gulf and the evolving nature of its domestic politics. As constituencies and alliances shift, and policies and positions alter within the corridors of clerical power, Washington has an opportunity to influence the direction of Iran's nuclear deliberations before decisive steps are taken in the wrong direction. Through a bilateral arrangement involving mutual concessions from both sides, the US could empower those within the clerical estate calling for nuclear restraint. In dealing with Iran's nuclear crisis, US leadership and active engagement are indispensable.