(Reuters) - Nuclear power company Exelon Corp agreed to buy utility company Pepco Holdings Inc for more than $5.4 billion in cash, Bloomberg reported, citing people familiar with the transaction. Pepco, with a market capitalization of about $5.71 billion, operates utilities in Delaware, Maryland and New Jersey and serves about 2 million customers. The deal is expected to be announced as early as Wednesday morning, according to the report. (http://r.reuters.com/wav88v) Exelon and Pepco were not immediately available for comment outside regular U.S. business hours. Chicago-based Exelon struck a deal three years ago to buy rival Constellation Energy Group for $7.9 billion, in a bid to become the largest generator of competitively priced electricity in the United States. (http://r.reuters.com/bev88v) (Reporting by Arnab Sen in Bangalore; Editing by Gopakumar Warrier)