Bank of America (BoA) moved yesterday to enforce its controversial $21 billion (£10.6 billion) purchase of LaSalle bank in the United States from ABN Amro, filing an appeal with the Dutch Supreme Court.

BoA argued that American law, rather than Dutch, should govern the deal – a pivotal transaction in the €72 billion (£49 billion) battle for the Dutch bank ABN Amro – because the contract was drafted and signed in the US.

The future of the entire European banking landscape hinges on the legality of the deal, which was frozen two weeks ago by the Dutch commercial court pending a vote by ABN shareholders.

An agreed €64 billion takeover of ABN by Barclays is conditional on the “poison pill” deal going through. A rival €72 billion break-up approach by Royal Bank of Scotland, Banco Santander, of Spain, and Fortis, of Belgium, depends on its being unwound.

“We’re confident that the Dutch Supreme Court, when presented with all the facts, will overturn the [Amsterdam Superior Court’s] decision,” Scott Silvestri, a BoA spokesman, said.

BoA has also filed a suit against ABN in the New York Federal District Court to enforce its purchase of the Chicago-based bank, which it sees as the last piece in the jigsaw for its nationwide American franchise. Yesterday Barclays lodged its own appeal in defence of the LaSalle deal. ABN is also expected to appeal.

Hans de Savornin Lohman, a lawyer for Loyens & Loeff, which filed the appeal on behalf of BoA, said that he expected a ruling in the first week of July. For ABN employees and shareholders, this means at least seven further weeks of uncertainty.

VEB, the Dutch shareholder group, which has challenged ABN’s management, said that the appeal process could take six to nine months.

Barclays yesterday dismissed the RBS approach for ABN as “a ghost offer” and questioned its financing. Frits Seegers, chief executive of Barclays retail division, said: “There are currently two offers on the table: ours, and a ghost offer.”

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