Russia&#39;s President Vladimir Putin, left, reaches out to shake hands with U.S. President Barack Obama during arrivals for the G-20 summit at the Konstantin Palace in St. Petersburg, Russia on Thursday, Sept. 5, 2013. The threat of missiles over the Mediterranean is weighing on world leaders meeting on the shores of the Baltic this week, and eclipsing economic battles that usually dominate when the G-20 world economies meet. (AP Photo/Dmitry Lovetsky)