Guinness has asked Abbott Mead Vickers BBDO and Saatchi & Saatchi to pitch head-to-head for its global ad business.
Diageo-owned Guinness hopes the move will allow it to introduce and adapt creative work more quickly, although this will not necessarily lead to single creative ideas being used globally.
Guinness' global ad and promotional budget is worth pounds 230m. A decision on the appointment is due by the end of the year.
AMV, which handles Guinness in the UK, has received numerous creative awards for its work, including the 'Surfer' campaign.
Saatchis, which works for Guinness in Africa and the Caribbean, developed the Michael Power character and the tagline, 'Guinness brings out the power in you'.
The opportunity to win the global business throws up a potential conflict of interest for the agency in the UK. It also handles Carlsberg Tetley's pounds 22m UK advertising for brands including Castlemaine XXXX and Carlsberg.
The pitch marks the end of Guinness' relationship with HHCL & Partners, which handles its ad business in Ireland.
It will also lead to a split between Guinness and Ogilvy & Mather, which handles its business in Singapore and Malaysia; German ad firm Frohling Werbeagentur; and Weiss, Stagliano & Partners, which has the account in the US and Canada.
The pitch, which does not include media, is being overseen by Jon Potter, global brand director at Guinness.
Potter said: 'The more work we do globally, the more we recognise the commonalities that exist - we want to leverage those to boost growth.
'The Guinness brand is iconic; people respect it - even those who don't drink it. There is a big opportunity to make the brand more accessible.'