A pro-Russian rebel fighter guards an area of the Malaysia Airlines Flight 17 crash site in the village of Hrabove, Donetsk region, eastern Ukraine, earlier this week. Investigators erect a "no trespassing" sign in the background. Mstyslav Chernov/AP hide caption

itoggle caption Mstyslav Chernov/AP

Russian President Vladimir Putin looks to his side during the family photo session of the G-20 summit in Brisbane, Australia, on Saturday. Putin was sternly criticized by Western leaders over Moscow's involvement in eastern Ukraine. Rob Griffith/AP hide caption

itoggle caption Rob Griffith/AP

A pro-Russian separatist casts a ballot during the self-proclaimed Donetsk People's Republic leadership and local parliamentary elections at a polling station in the southern coastal town of Novoazovsk on Sunday. Maxim Zmeyev/Reuters/Landov hide caption

itoggle caption Maxim Zmeyev/Reuters/Landov

Ukrainian lawmakers applaud a televised address by the President of the European Parliament Martin Schulz (on screen) in the Ukrainian parliament on Tuesday in Kiev. The parliament voted to strengthen trade ties with the EU, but not until 2016. Sergey Dolzhenko/EPA/Landov hide caption

itoggle caption Sergey Dolzhenko/EPA/Landov

Smoke rises near Donetsk's airport on Sunday amid increased shelling. Pro-Russian forces are trying to dislodge Ukrainian troops. The renewed fighting is testing a fragile cease-fire. Philippe Desmazes/AFP/Getty Images hide caption

itoggle caption Philippe Desmazes/AFP/Getty Images

Many students at Kiev's Lyceum for the Humanities have relatives in Russia or parts of eastern Ukraine controlled by separatists. The conflict has divided families and caused many problems, they say, but it has also strengthened their sense of Ukraine's identity. Eleanor Beardsley/NPR hide caption

itoggle caption Eleanor Beardsley/NPR

Mothers and wives of Russian paratroopers captured in Ukraine wait for information outside their base in Kostroma, Russia. Russia's military has been challenged to explain an upsurge in dead and missing soldiers from its elite units. Dmitry Serebryakov/AFP/Getty Images hide caption

itoggle caption Dmitry Serebryakov/AFP/Getty Images

President Obama stands alongside British Prime Minister David Cameron, center left, NATO Secretary General Anders Fogh Rasmussen, second left, Croatian President Ivo Josipovic, left, Romanian President Traian Basescu, right, and RAF Group Captain David Bentley, second right, during a flypast at the NATO summit at the Celtic Manor Resort in Newport, Wales on Friday. Jon Super/AP hide caption

itoggle caption Jon Super/AP

President Obama sits with (from left) French President Francois Hollande; Ukrainian President Petro Poroshenko; British Prime Minister David Cameron; German Chancellor Angela Merkel; and Italian Prime Minister Matteo Renzi as they meet about Ukraine Thursday at the NATO summit at Celtic Manor in Newport, Wales. Charles Dharapak/AP hide caption

itoggle caption Charles Dharapak/AP