Royal Bank of Scotland
The group of RBS, Spain's Santander
That would value the Dutch bank at about 72 billion euros and would make it the biggest bank takeover.
The proposals would trump an all-share offer of about 66 billion euros for ABN from Barclays
These include making the purchase of LaSalle conditional on also buying the rest of ABN. Sources have said this would effectively mean the consortium would be paying itself, so they can make a high bid for the business.
The offer for ABN is also conditional on the consortium not being exposed to any litigation related to the sale of LaSalle, the sources said.
Bank of America on Friday sued ABN, seeking damages and a court injunction to block the sale of LaSalle to a rival bidder.
The funding of the consortium's offer has not yet been finalized, the sources said. They said under the proposals put forward funding may not be completed until the fourth quarter, partly as Fortis shareholders may need to vote on the deal and raise cash through a big rights issue.
Some 70% of the consortium's offer for ABN would be in cash -- about 50 billion euros -- and the remaining 30% would be in RBS shares, in line with a plan outlined by the group two weeks ago.
The fight for both LaSalle and ABN has become increasingly complex.
The Dutch bank agreed to be taken over by Barclays and at the same time announced the sale of LaSalle.
Some shareholders claimed the LaSalle deal was a "poison pill" to make it harder for the RBS-led consortium to make a counterbid for ABN, and on Thursday a Dutch court froze the LaSalle sale and said it should be voted on by ABN shareholders.
Under the original LaSalle deal counterbidders had until midnight on Sunday in New York to beat Bank of America's offer under a "go shop" agreement. The RBS-led group, wary of the implications of a legal battle, has therefore proceeded with its plans to bid for LaSalle as well as moving for all of ABN.
Executives from the three banks have been in talks with ABN's management for the past two days to flesh out details. Talks will continue on Sunday, one source said.
ABN, RBS and Barclays all declined to comment.