The plan is designed to curtail the financial freedom of every Iranian official, individual and entity the Bush administration considers connected not only to nuclear enrichment efforts but to terrorism, government corruption, suppression of religious or democratic freedom, and violence in Iraq, Lebanon, Israel and the Palestinian territories. It would restrict the Tehran government's access to foreign currency and global markets, shut its overseas accounts and freeze assets held in Europe and Asia.

The United States, which has imposed unilateral sanctions on Iran for nearly three decades, would shoulder few of the costs of its ambitious new proposal, but internal U.S. assessments suggest that the sanctions could not hurt Tehran without causing significant economic pain for Washington's friends. That calculation has made the plan a difficult sell, especially in capitals such as Rome and Tokyo, which import significant quantities of Iranian oil.