US credit card issuer Visa Inc. said Monday it was to buy back its former subsidiary Visa Europe in a 21.2-billion-euro ($23.5-billion) deal.

The deal, approved by both boards, will be carried out in two stages -- an initial payment of 16.5 billion euros followed by a possible additional payment of 4.7 billion euros four years after the agreement is finalised, Visa said.

UK-incorporated Visa Europe, operated by member banks and other payment service providers from 38 countries, has been operating independently of Visa Inc since 2004.