It took seven years to reach the proposed $7.25 billion antitrust settlement involving Visa Inc., MasterCard Inc., the country's biggest banks and millions of retailers.

Now, the courtroom battle for a judge's approval of the high-stakes agreement has begun -- and it's the fight among the retailers themselves taking center stage.

Lawyers for the retailer class on Friday filed their motion for preliminary approval of the agreement in federal court in Brooklyn, N.Y. But 10 of the 19 named merchant plaintiffs now oppose it, including such groups as the National Retail Federation and National Association of Convenience Stores.

Minneapolis-based Target and discount giant Wal-Mart, neither of whom are named plaintiffs in the case, also have spoken out against it.

The agreement aims to settle accusations by retailers that the banks and card companies illegally colluded to fix credit card interchange fees at a high rate, gouging merchants across the country and costing consumers billions of dollars. It would pay $6.05 billion to store owners for alleged past damages, with the rest coming from a temporary reduction in interchange fees called swipe fees.

No date for a hearing has been set, but one is likely to be held by the end of January, said K. Craig Wildfang, a partner at Robins, Kaplan, Miller & Ciresi in Minneapolis and co-lead counsel for the class plaintiffs, which covers about 7 million retailers. Interested parties have 30 days to file their opposition.

The named banks, which include Wells Fargo & Co., and card companies have been quiet. But some of the retailers have been howling since the settlement was announced in July, arguing that it doesn't fix a "cartel-like system" and won't prevent swipe fees from rising higher.

Within minutes of the filing Friday, retailers again were assailing the proposal.

"Retailers would rather take their chances in court than accept this one-sided swindle written by the card industry for the card industry," said National Retail Federation general counsel Mallory Duncan in a news release.

Ditto for the Retail Industry Leaders Association (RILA), which called the deal "unacceptable in every way."

"Retailers overwhelmingly view this proposal not as a settlement, but as surrender," said RILA President Sandy Kennedy in a statement.

The protest now officially goes to the courtroom of U.S. District Judge John Gleeson in New York, who is no stranger to such disputes. He presided over a similar long-running class-action merchant antitrust lawsuit that pitted retailers led by Wal-Mart Stores Inc. against Visa and MasterCard. That case was settled in 2005 in the retailers' favor for about $3.05 billion.

If this proposed settlement is approved for $7.25 billion, it would be the largest antitrust settlement ever, said Bert Foer, head of the nonprofit American Antitrust Institute in Washington. Foer has said the case is as much about consumers as retailers, because the fees stores have to pay the banks and credit card networks hit consumer pocketbooks in higher prices.

Three of the original plaintiffs are Minnesota businesses: St. Cloud-based grocer Coborn's Inc., St. Louis Park-based Traditions Classic Home Furnishings and CHS Inc. in Inver Grove Heights, the country's largest agricultural cooperative.

Wildfang has steadfastly maintained that the agreement announced July 13 is the best possible resolution and creates meaningful reform. Among other things, it enables merchants to form buying groups to negotiate more favorable commercial terms with the card networks, he said.

It also allows retailers to influence how their customers pay for goods by offering discounts for using low-cost cards or cheaper forms of payment such as cash, or by adding surcharges for high-cost cards.

In a news release, Wildfang credited the litigation with driving the largest card-issuing banks to divest their ownership and control of Visa and MasterCard, so that the two are now overseen by independent boards of directors and answer to public shareholders.

In an interview, Wildfang called the retail opposition "much ado about nothing."

"I think the court will come through with the settlement at the end of the day," Wildfang said. "A few loud voices in Washington have managed to scare a lot of people."

St. Paul resident Michael Schumann, co-owner of Traditions Classic Home Furnishings, said he understands the frustrations of the big retail groups but supports the settlement. "I don't see the opposition to this having put on the table any alternatives," he said.

Schumann said he thinks the big retail groups ultimately don't support the settlement because what they are seeking is a "Durbin II" for the credit card industry, referring to the part of the Dodd-Frank financial reform act that capped fees on debit card swipe fees. "I would love that," he said. "But I'm skeptical they're going to get it."

Jennifer Bjorhus • 612-673-4683