E-Trade Financial Corp. is in discussions with TD Bank Financial Group about acquiring the U.S. operations of its TD Waterhouse discount-brokerage unit, analysts say. The combined entity would have about 5 million customer accounts, placing it ahead of Ameritrade Holding Corp., which has 3 million accounts, but behind discount brokerage leader Charles Schwab & Co., which has 8 million accounts. E-Trade confirmed in a statement that it's holding talks with TD Bank but said neither side would comment further until a deal is consummated.