There's increased uncertainty in Europe over the future of the common currency, the euro. The central problem is that some euro users, such as Greece, have weak economies while others, such as Germany, have strong ones. Michael Probst/AP hide caption

itoggle caption Michael Probst/AP

For the first seven years of the war in Afghanistan, almost all U.S. and NATO supplies were trucked overland to Afghanistan through parts of Pakistan effectively controlled by the Taliban. Here, smoke and flame rise from a burning NATO supplies oil tanker after armed militants torched the tankers in Mithri, Pakistan, in February. STR/AFP/Getty Images hide caption

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German Chancellor Angela Merkel and French President Nicolas Sarkozy met in Berlin last month for negotiations on the European debt crisis. They meet again on Tuesday in Paris in another attempt to stabilize the faltering economies in the eurozone. Ferdinand Ostrop/AP hide caption

itoggle caption Ferdinand Ostrop/AP

Spanish Prime Minister Jose Luis Rodriguez Zapatero is seen before a Cabinet meeting in Madrid on July 22. Spain is in the midst of an economic crisis. Daniel Ochoa de Olza/AP hide caption

itoggle caption Daniel Ochoa de Olza/AP

A soldier participates in a military exercise conducted by Georgians and U.S. Marines together on Friday. As the U.S. faces cuts to military spending, it's hoping to share more of its defense burden with European allies. Shakh Aivazov/AP hide caption

itoggle caption Shakh Aivazov/AP