James M. Lindsay argues that while the United States remains the most significant military, diplomatic, and economic power in a changing geopolitical environment, it faces increasing difficulty in driving the global agenda.

Despite international pressure, Iran appears to be continuing its march toward getting a nuclear bomb.

America Unbound argues that President Bush has redefined how America engages the world, shedding the constraints that friends, allies, and international institutions have traditionally imposed on its freedom, insisting that an America unbound is a more secure America.

A preview of world events in the coming week from CFR.org: Nawaz Sharif to be sworn in as Pakistan's prime minister; Vice President Joe Biden visits Brazil, Colombia and Trinidad & Tobago; And Memorial Day is observed in the US.

A preview of world events in the coming week from CFR.org: The US debt ceiling suspension expires; the African Union summit takes place in Addis Ababa; and East Timor celebrates its 11th anniversary of independence.

A preview of world events in the coming week from CFR.org: Turkey's Prime Minister visits the White House; Israel celebrates National Day while Palestinians mark al-Nakba; The Arctic Council meets in Sweden; and the Cannes film festival kicks off in France.

A preview of world events in the coming week from CFR.org: U.S. president Barack Obama visits Mexico and Costa Rica; Japanese prime minister Shinzo Abe heads to Russia; and tensions persist over the East China Sea.

A preview of world events in the coming week from CFR.org: Investigations into the Boston Marathon explosions continue; King Abdullah II of Jordan visits the United States; and the ASEAN summit takes place in Brunei.

A preview of world events in the coming week from CFR.org: Britain honors the late Margaret Thatcher; Venezuelans select the successor to Hugo Chavez; and the World Bank and IMF spring meetings begin in Washington.

A preview of world events in the coming week from CFR.org: U.S. Secretary of State John Kerry visits South Korea, Japan and China; President Obama submits a budget to Congress; and the re-trial of ousted Egyptian president Hosni Mubarak begins in Cairo.

A preview of world events in the coming week from CFR.org: Pakistan prepares for a government transition; the BRICS summit takes place in South Africa; and the annual Arab League summit convenes in Doha.

A preview of world events in the coming week from CFR.org: President Obama visits Israel; Iran's supreme leader delivers a speech for Iranian New Year; the 10th anniversary of the U.S. invasion of Iraq is marked; and China's new president visits Russia.

A preview of world events in the coming week from CFR.org: Venezuela ponders life after Chavez; the U.S. Senate Armed Services committee debates strategic and cyber command; Russia's trial of deceased lawyer Sergei Magnitsky begins; and Tibetan Uprising Day is observed.

A preview of world events in the coming week from CFR.org: Kenya holds presidential and parliamentary elections; Italy tries to sort out its post-election stalemate; and the 60th anniversary of death of Stalin is marked.

The United States has cut defense spending in the past, and it is doing so again today. In 1989, for example, the Defense Department spent $295 billion; seven years later it spent $253 billion, or about 14 percent less in nominal dollars. When inflation is taken into account, defense spending dropped by more than 25 percent during the 1990s. U.S. defense spending will likely follow a similar trajectory over the next decade with the Afghanistan war ending and pressure mounting to cut government spending.

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A preview of world events in the coming week from CFR.org: Italy holds general elections; NATO defense ministers meet in Brussels; and the UN Security Council debates North Korea sanctions.

A preview of world events in the coming week from CFR.org: Barack Obama delivers his fourth State of the Union Address; European Central Bank head Mario Draghi speaks before the Spanish Parliament; and Bahrain leadership and opposition meet for possible negotiations.

A preview of world events in the coming week from CFR.org: the European Union hosts an international meeting on Mali; Egypt hosts the twelfth Organization of Islamic Cooperation summit; and parliamentary elections for Cuba take place.

A preview of world events in the coming week from CFR.org: Confirmation hearings begin for President Obama's initial round of cabinet nominees; Vice President Joe Biden attends the Munich Conference; and the WTO seeks its next director-general.

A preview of world events in the coming week from CFR.org: U.S. President Barack Obama is sworn in for a second term; Japanese Prime Minister Shinzo Abe visits Asean nations; and Israel and Jordan hold elections.

A preview of world events in the coming week from CFR.org: United States considers complete Afghan troop withdrawal; the Colombian government and FARC rebels hold peace talks; and the North American International Auto Show gets underway.

A preview of world events in the coming week from CFR.org: The World Economic Forum publishes its annual Global Risks Report; Venezuela's presidential inauguration is clouded by illness; and the United States and Russia hold talks with the international envoy to Syria.

In this interview, CFR's James Lindsay discusses three major foreign policy challenges confronting the United States in 2013, including tumult in the Middle East, rising tensions in East Asia, and the U.S. fiscal cliff.