U.S. President Barack Obama (R) walks with Polish President Bronislaw Komorowski during a welcome ceremony at the Presidential Palace in Warsaw May 28, 2011. Obama lauded Poland on Saturday as a key U.S. ally whose democracy and economic prosperity can serve as a model for neighbouring former Soviet republics such as Ukraine and Belarus. REUTERS/KPRP/Wojciech Grzedzinski/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