The move surprised analysts who considered that Goldman was more likely to act in an advisory capacity for Royal Bank of Scotland (RBS) in any counter bid it may make.
Goldman Sachs will now join Morgan Stanley, Lehman Brothers, UBS and Rothschild as advisors to ABN Amro.
Meanwhile, JP Morgan Cazenove, Citigroup, Deutsche Bank, Lazard and Credit Suisse are all involved in Barclays bid.
Should RBS still be looking to launch a counter bid it is now deemed likely to turn to Merrill Lynch, which is currently not affiliated to any party in the Barclays ABN Amro deal, and with which the head of RBS Sir Fred Goodwin enjoys a good relationship.
The terms of the deal under which Barlcays and ABN Amro are currently negotiating stipulate that the period during which Barclays has the exclusive right to discuss terms with the Dutch bank it is to end next Friday.