CVS, the US drugstore chain, has thrown down the gauntlet in its battle to win pharmacy benefits manager Caremark Rx by raising its offer to match that of rival bidder Express Scripts.

CVS increased its offer to $26.3bn (€34.4bn), the same as Express Scripts offered less than a day before. Caremark's board, which has long favored the CVS bid, approved the offer and it should face a shareholder vote today.