Aib is the latest Irish bank to put a portion of its loan book up for sale, after launching a process to sell a €675m (£539m) portfolio of commercial property loans.
The debt is understood to be backed by commercial property in Ireland, including Dublin office space. The loans are being sold through US investment bank Morgan Stanley, according to a report in the Financial Times.
The FT said the portfolio, known as Project Kildare, is being touted to global "vulture funds" and private equity firms.
The loans are some of the €24bn (£19.15m) of AIB commercial property loans that were not transferred to Nama.
AIB along with the other banks is under pressure to sell such 'non-core' assets in order to clean up its balance sheets, to free up money for traditional lending to business and consumers. Analysts say the latest crisis with banks in Spain means the window for such sales could be starting to narrow.