The banks involved seem to be narrowing down to La Salle in Chicago as a key component in the merger stakes. 

John Varley, Barclays’ chief executive, has received several expressions of interest in La Salle, ABN’s Chicago-based retail bank, including one from Bank of America. BNP Paribas, Wachovia and Citigroup are also thought to be interested in the business, which is worth about £5bn.

By selling the American business, Barclays believes it could come close to matching any rival offer for ABN that emerges from a consortium of Royal Bank of Scotland, Santander and Fortis.

Source: Barclays plays ABN trump card | Business | Money | Telegraph

I also understand BMO Bank of Montreal have expressed interest in La Salle.