European Union foreign policy chief Catherine Ashton (L) and Iranian Foreign Minister Mohammad Javad Zarif smile at the start of a conference in Vienna March 18, 2014. Iran and six world powers will try to make headway toward resolving their nuclear dispute in talks that started in Vienna on Tuesday, with Western officials hoping the challenge will not be made even more difficult by the Ukraine crisis. The United States and European Union have imposed sanctions including asset freezes and travel bans on some senior Russian and Ukrainian officials after Crimea applied to join Russia on Monday following a secession referendum. REUTERS/Heinz-Peter Bader (AUSTRIA – Tags: POLITICS ENERGY TPX IMAGES OF THE DAY)