A consortium of banks led by Royal Bank of Scotland could lower the level of acceptances needed to buy Dutch bank ABN AMRO to a simple majority, it said on Friday.

The consortium, which also includes Spain's Santander and Belgian-Dutch group Fortis, currently requires 80 percent of ABN shareholders to accept its offer for it to be declared unconditional.

The trio are set to win the long-running takeover battle for ABN with their offer of about 70 billion euros ($99 billion), which would be the biggest ever bank takeover.

The consortium said in a statement it reserves the right to lower the minimum acceptance condition for its offer to a majority of the issued shares.

It is required to give five days notice of any potential change to the offer terms. The offer is due to close at 1500 Amsterdam time (9 a.m. EDT) on October 5.

The consortium's offer is currently worth about 37.85 euros per ABN share, 20 percent higher than the value of a rival offer from Britain's Barclays.

By 4:15 a.m. ABN shares were up 0.1 percent at 36.95 euros.