A police officer stands guard Wednesday near a Christmas market in Berlin where a truck plowed into a crowd Monday, killing 12 people. Sean Gallup/Getty Images hide caption

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Sean Gallup/Getty Images

German Chancellor Angela Merkel at a session of the Bundestag Lower House of Parliament in Berlin Wednesday. Germany's top federal prosecutor told legislators today that he is opening a formal inquiry into allegations that the NSA tapped her phone. John MacDougall/AFP/Getty Images hide caption

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John MacDougall/AFP/Getty Images

Victoria Nuland, the U.S. assistant secretary of state, lights a candle in St. Michael Cathedral in Kiev, Ukraine, on Thursday. Her comments during a leaked phone call have sparked a diplomatic row. AP hide caption

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AP

President Obama and Chancellor Angela Merkel during the official arrival ceremony for the German leader at the White House this morning (June 7, 2011). Jewel Samad /AFP/Getty Images hide caption

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Jewel Samad /AFP/Getty Images