American Express has teamed up with UK private equity firm Permira to join the battle for the Royal Bank of Scotland's WorldPay payment processing business, according to the Financial Times.
French IT giant Atos Origin has also entered the fray for the £2.5 billion rated unit, partnering PE firms CVC Capital Partners and Welsh Carson Anderson & Stowe, says the FT.
Around six bidders are still in the hunt for the business, which RBS is being forced to sell by the European competition authorities as a condition for joining the UK government's asset protection scheme.
Canadian card payment processor Moneris Solutions is in the running while four private equity bids - from CVC, TPG, Warburg Pincus and a joint effort by Advent International and Bain Capital are also on the table.
Citing sources, the FT says RBS is indicating that PE firms should team up with partners that have experience in the field, giving an edge to Advent, which last year acquired a 51% stake in the payments processing business of Fifth Third Bancorp and Warburg Pincus, which has a minority stake in Fidelity National Information Services.
Second-round bids are due by 31 May.
American Express in move for RBS arm - FT