U.S. President Barack Obama and Poland’s President Bronislaw Komorowski participate in a welcome ceremony at the Presidential Palace in Warsaw May 28, 2011. REUTERS/Handout (POLAND – Tags: POLITICS) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS