The deal comes as Europe's financial sector braces for lean times. With banks' profitability in recent years already dented by low interest...

Does a larger, even potentially world-scale bank mean a more efficient bank?

Banks have shut about 20,000 branches across Europe in the last four years, including 5,500 last year and 7,200 in 2011.

Spain is under increasing pressure to find a quick way to save its troubled banking sector from collapse.