T he U.S. invasion of Iraq has stirred up sectarian tensions well beyond Iraq’s borders and destroyed the regional balance of power that had existed between a theocratic, Shia-led Iran and the secular, Sunni-led regime of Saddam Hussein. As the United States extracts itself from a mess of its own making, the key challenge facing Washington is to stand up regional sources of stability as U.S. forces stand down. To attain this objective, the United States must devolve more strategic responsibility to local actors while it simultaneously seeks to catalyze regional integration as a foundation for stability. Ideally, regional integration and cooperation, not the balance of power or democratization, should become the focus of American strategy. Assuming that Iraq’s internal troubles will for the foreseeable future prevent Baghdad’s return to adventurism, Iranian ambition will remain the primary impediment to such pan-regional cooperation. Washington should therefore put a premium on engaging Tehran, seeking to transform it from a regional threat into a net contributor to security. As in Europe, South America, Southeast Asia, and elsewhere, rapprochement between traditional rivals, regional integration, and the development of a cooperative security architecture offer the best hope for a lasting stability in the Persian Gulf.