The United States has long been a leader in using sanctions to discourage unwanted behavior by other countries, including terrorism and human rights abuses. But the erosion of U.S. economic predominance has undermined Uncle Sam's ability to wield the sanctions weapon. With more countries producing essential items, the threat of a cutoff of U.S. goods and services is far less daunting than it once was. Nor is the American consumer market such a vital outlet for other nations' exports. As unilateral U.S. sanctions pose less of a threat, the United Nations is increasingly using sanctions to preserve international peace. Some experts say a new U.N. agency is needed to enforce multilateral sanctions in the post-Cold War era.