NEW YORK — A federal judge said she’s not likely to approve the $30 billion settlement between the payment processing giants Visa and Mastercard and the merchants who say they’ve overpaid on swipe fees.

Visa and Mastercard reached a settlement with a group of small businesses and merchants back in March. The deal would lower and cap the fees charged by Visa and Mastercard and allow small businesses to collectively bargain for rates with the payment processors in a similar way that the large merchants do on their own now.

But the settlement was not universally accepted. The National Retail Federation, the largest U.S. retail trade group, said it was likely to oppose the settlement, saying the relief was only temporary and that payment processing fees remain too high. The settlement would have capped swipe fees for five years, which merchants opposed to the settlement said was insufficient.

In a brief order, Judge Margo Brodie of the Eastern District of New York said she was unlikely to grant final approval to the settlement. The decision means that, absence a settlement, the case could go to trial.

The settlement stems from a 2005 lawsuit that alleged merchants paid excessive fees to accept Visa and Mastercard credit cards, and that Visa, Mastercard and their member banks acted in violation of antitrust laws. Visa and Mastercard collect a fee from every transaction that runs on their network. The fee varies depending on the size of the merchant as well as the industry they operate in, but generally it’s between 1% and 3% of a transaction’s value.

In 2018 Visa and Mastercard agreed to pay $6.2 billion as part of the long-running suit filed by a group of 19 merchants. But the lawsuit then had two pieces that needed to be resolved: a dispute over the rules Visa and Mastercard impose to accept their cards, and the merchants who chose not to participate in the settlement.