1/5Ukrainian businessman, politician and presidential candidate Petro Poroshenko (L) meets supporters during his election campaign in Odessa May 21, 2014. REUTERS/Mykola Lazarenko/Pool (UKRAINE - Tags: BUSINESS POLITICS ELECTIONS) - RTR3Q6BH
U.S. Vice President Joe Biden has warned that the United States could impose tougher sanctions on Russia if it undermines Ukraine's presidential elections on May 25.
2/5Local residents walk with their young children in a park in Donetsk, Ukraine, on Wednesday, May 21, 2014. Ukraine are hold a presidential election on Sunday(AP Photo/Evgeniy Maloletka)
U.S. Vice President Joe Biden has warned that the United States could impose tougher sanctions on Russia if it undermines Ukraine's presidential elections on May 25.
3/5Workers stand near pipes at a gas compressor station near Uzhhorod May 21, 2014. Russia has said state-controlled exporter Gazprom will not supply transit nation Ukraine with gas for its own use in June if Kiev fails to pay in advance and has warned a cut
U.S. Vice President Joe Biden has warned that the United States could impose tougher sanctions on Russia if it undermines Ukraine's presidential elections on May 25.
4/5Ukrainian businessman, politician and presidential candidate Petro Poroshenko (R) meets supporters during his election campaign in Odessa May 21, 2014. REUTERS/Mykola Lazarenko/Pool (UKRAINE - Tags: POLITICS ELECTIONS BUSINESS) - RTR3Q6BD
U.S. Vice President Joe Biden has warned that the United States could impose tougher sanctions on Russia if it undermines Ukraine's presidential elections on May 25.
5/5Former Ukrainian prime minister and current presidential candidate Yulia Tymoshenko (L) visits a hospital during her election campaign in the city of Sumy May 21, 2014. Campaigning for Ukraine's presidential election, Tymoshenko says she alone can save th
U.S. Vice President Joe Biden has warned that the United States could impose tougher sanctions on Russia if it undermines Ukraine's presidential elections on May 25.
