The battle for ABN Amro isn't over yet. On Wednesday, a banking consortium led by Royal Bank of Scotland sought to break up the deal announced with Barclays on Monday. The banks offered $99 billion for ABN Amro, which they claim is 13 percent more than Barclays' bid.

However, this new offer hinges on breaking up the deal ABN made to sell its American unit, LaSalle Bank, to Bank of America for $21 billion. The consortium wants LaSalle to remain within ABN.

R.B.S., which is joined by Fortis and Santander Central Hispano, offered to pay 70 percent of its bid in cash, which to some shareholders will be more attractive than Barclays' stock offer. The remaining 30 percent would be in R.B.S. stock. A hedge fund called The Children's Investment Fund Management, which owns nearly 3 percent of ABN's shares, called the new offer compelling, and recommended the board accept it if the LaSalle deal can be terminated.

Barclays will now weigh a counterbid, and if the LaSalle deal can indeed be terminated, Bank of America will have the opportunity to make a higher offer. In addition, other European banks could still enter the fray.

Shares of ABN stock rose 4.6 percent in trading in Amsterdam on Wednesday.