A convoy of U.N. vehicles with chemical weapons experts on board head out on Friday to do more work as the investigate allegations of chemical weapons use in near Damascus. Louai Beshara /AFP/Getty Images hide caption

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A Free Syrian Army fighter looks through the scope of his sniper rifle at an area controlled by forces loyal to President Bashar Assad in Aleppo. Reuters/Landov hide caption

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In Washington, D.C., this week, there have been demonstrations both in favor of and against a military strike on targets in Syria. Outside the White House on Monday, supporters of Syrian President Bashar Assad waved a Syrian flag with his face on it. Jewel Samad/AFP/Getty Images hide caption

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Vice President Joe Biden stands in front of his residence at the Naval Observatory in Washington, D.C., on Sunday, as President Obama arrives at a dinner Biden is hosting for Republican senators. Charles Dharapak/AP hide caption

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Sen. John McCain, R-Ariz., and Sen. Lindsey Graham, R-S.C., met with President Obama on Sunday at the White House. Jewel Samad /AFP/Getty Images hide caption

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Lindsay Graham, R-S.C., right, accompanied by Sen. John McCain, R-Ariz., speaks Monday following a White House meeting with President Obama. Both senators are calling for a tough military response against Syria. Pablo Martinez Monsivais/AP Photo hide caption

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Syrian activists — many wearing gas masks — looked for victims and evidence Thursday in an area near Damascus where government forces allegedly used chemical weapons. Reuters/Landov hide caption

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Russian President Vladimir Putin (right) and British Prime Minister David Cameron met earlier this month. Cameron said then that he was encouraged by Russia's willingness to take part in a peace conference on Syria. Now, Russia is said to be angry about the EU's decision to lift an embargo on arming the Syrian opposition. Alexey Nikoksky /AFP/Getty Images hide caption

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British Prime Minister David Cameron (left) and Russian President Vladimir Putin viewed the Sochi Olympic Park along the Black Sea coast by helicopter Friday. Nikolsky Alexei /ITAR-TASS /Landov hide caption

itoggle caption Nikolsky Alexei /ITAR-TASS /Landov