Russian President Vladimir Putin as he answered questions on national TV Thursday in Moscow. Alexey Nikolsky/RIO Novosti/Kremlin pool/EPA/Landov hide caption

toggle caption Alexey Nikolsky/RIO Novosti/Kremlin pool/EPA/Landov

A Russian armored vehicle on the road between Simferopol and Sevastopol in Crimea earlier this month. Russia annexed the region two weeks ago. Other Russian forces, across the border from Ukraine, may pull back in coming days. Viktor Drachev/AFP/Getty Images hide caption

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President Obama, accompanied by Dutch Prime Minister Mark Rutte, speaks during their joint news conference at the conclusion of the Nuclear Security Summit in The Hague on Tuesday. Pablo Martinez Monsivais/AP hide caption

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Armed men stood atop a chimney near Ukraine's naval headquarters in Sevastopol, Crimea, on Wednesday. They raised Russian flags after taking over much of the facility. Vasily Fedosenko /Reuters /Landov hide caption

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Russian President Vladimir Putin. Mikhail Klimentyev/RIA Novosti/Kremlin pool /EPA/Landov hide caption

toggle caption Mikhail Klimentyev/RIA Novosti/Kremlin pool /EPA/Landov

A masked man, believed to be a Russian soldier, holds a Crimean flag as members of a pro-Russian self-defense unit stand in formation Monday in the regional capital of Simferopol. Vasily Fedosenko /Reuters /Landov hide caption

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Troops under Russian command scream orders to turn back before firing warning shots at the Belbek airbase in Crimea. The troops were reacting to a large group of unarmed Ukrainian troops who approached them. Sean Gallup/Getty Images hide caption

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