It seems unlikely that the plot to kill a Saudi ambassador involved the highest levels of Iran's government, says expert Kenneth Katzman, including the plan to use non-Muslim proxies to carry it out.

The U.S. government designates Iran as the "most active state sponsor of terrorism," which feeds concerns about Iran's growing nuclear program.

Stewart M. Patrick, Director of the Council on Foreign Relations' International Institutions and Global Governance Program, explains why some weak and failing states such as Pakistan are more attractive than others as safe havens for transnational terrorist groups.

In the event of a successful terrorist attack by Pakistan-based militants, U.S. actions toward Pakistan are limited, but the United States can help Pakistan intensify its fight against extremism, says South Asia security expert Bruce Riedel.

The U.S. State Department continues to list Cuba as a state sponsor of terror, though most experts say the country no longer poses a threat to U.S. national security.

Gary Samore, who was active in nuclear diplomacy with North Korea in the Clinton administration, says the latest agreement between the United States and North Korea is only a "very modest step forward" because it allows the next administration to proceed further in seeking a nuclear-disarmed North Korea.

Despite its recent willingness to combat terrorism, Sudan is still considered a state sponsor because of its ties to Hamas, the Iraqi insurgency, and violence in Darfur.

Max Boot looks at which presidential candidate “an Ahmadinejad, Assad or Kim would fear the most.”

The SEC’s new terrorism blacklist provokes anger from some major global companies and raises questions about the value of terror lists more generally.

Iranian expert Kaveh L. Afrasiabi says pressure by the United States on Tehran may backfire and will not push Tehran to give up its nuclear program.

Libya, for years a thorn in the side of U.S. policymakers, has boosted its profile in recent years, renouncing terrorism and abandoning its WMD. In response, the U.S. State Department has removed Libya from its list of state sponsors of terrorism and plans to resume normal diplomatic relations.

Libya's abandonment of its WMD program was a major foreign policy win for the Bush administration. Having resumed diplomatic ties with the one-time rogue, U.S. officials are hoping for similar results with Iran and North Korea.

North Korea's recent nuclear program and recent nuclear test have resulted in on-going negotiations aimed at North Korea's cooperation with the international community.