Online discount brokers Ameritrade Holdings Corp. (AMTD) and TD Waterhouse USA (search) are discussing a possible merger, the companies said on Tuesday.

In a brief statement, TD Waterhouse, a unit of Canadian bank Toronto Dominion (search), and Ameritrade said talks were under way and they would not have any further comment until a definitive agreement was reached. They said there were no assurances a deal would be consummated.

The Financial Times reported that the companies were close to a deal. It cited unnamed sources as saying the deal being discussed was structured as a takeover of TD Waterhouse by Ameritrade valued at $2 billion to $3 billion.

E+Trade Financial Corp. (ETRD) approached Ameritrade earlier this month with a takeover offer, but Omaha, Neb.-based Ameritrade rebuffed the bid.

Media reports said E+Trade's offer was designed to disrupt a possible union between Ameritrade and TD Waterhouse.