NEW YORK (Standard&Poor's) May 27, 2011--Standard&Poor's Ratings Services said today that it has assigned its 'BBB+' issue-level rating to Union Pacific Corp.'s new senior unsecured notes due 2022. On May 23, 2011, the company announced an offer to exchange certain debt securities. The proposed new note issue will not exceed $750 million. The final size of the notes offering is pending the results of the exchange offer. The ratings on Omaha, Neb.-based Union Pacific reflect the favorable risk characteristics of the U.S. freight railroad industry, as well as the company's solid competitive position, moderate financial policies, and strong liquidity. Price competition from other railroads and trucking companies in selected commodities and the capital intensity of the