The 21st century will be defined by security threats unconstrained by borders--from climate change, nuclear proliferation, and terrorism to conflict, poverty, disease, and economic instability. The greatest test of global leadership will be building partnerships and institutions for cooperation that can meet the challenge. Although all states have a stake in solutions, responsibility for a peaceful and prosperous world will fall disproportionately on the traditional and rising powers. The United States, most of all, must provide leadership for a global era.

U.S. domestic and international opinions are converging around the urgent need to build an international security system for the 21st century. Global leaders increasingly recognize that alone they are unable to protect their interests and their citizens-national security has become interdependent with global security.

Just as the founders of the United Nations and Bretton Woods institutions after World War II began with a vision for international cooperation based on a shared assessment of threat and a shared notion of sovereignty, today's global powers must chart a new course for today's greatest challenges and opportunities. International cooperation today must be built on the principle of responsible sovereignty, or the notion that sovereignty entails obligations and duties toward other states as well as to one's own citizens.

The US Presidential election provides a moment of opportunity to renew American leadership, galvanize action against major threats, and refashion key institutions to reflect the need for partnership and legitimacy. Delays will be tempting in the face of complex threats. The siren song of unilateral action will remain—both for the United States and the other major powers.

To build a cooperative international order based on responsible sovereignty, global leaders must act across four different tracks.

1. U.S. Engagement: Restoring Credible American Leadership
2. Power and Legitimacy: Revitalizing International Institutions
3. Strategy and Capacity: Tackling Shared Threats
4. Internationalizing Crisis Response: Focus on the Broader Middle East