The settlement, reached earlier this month, had been considered a victory for retailers. It settled a lawsuit alleging that card issuers conspired to fix merchants' fees for accepting credit cards.
Under the settlement, stores will be allowed to charge customers more if they pay with a credit card.
But the world's largest retailer said Tuesday that the settlement doesn't restrict credit card issuers from continually raising fees merchants must pay when shoppers use their cards. The Bentonville, Ark., company also says the settlement would require retailers to waive their rights to take action against card issuers.