Visa Inc. and MasterCard Inc. are close to settling a Justice Department antitrust probe over credit card acceptance rules, the Wall Street Journal reported on Sunday, citing people familiar with the negotiations.

The settlement, which could potentially give merchants more flexibility to steer customers to cards with lower processing fees, could be announced early this week, the newspaper said.

Merchants have long complained about the fees that they pay each year to accept and process credit cards.

At issue are the varied processing fees that the card companies charge merchants when customers use different cards. Cards that offer rewards such as airline miles cost merchants more, and merchants who agree to accept a company's cards must accept all of them.

The Justice Department investigation, which Visa and MasterCard disclosed in late 2008, involves card-company policies that prevent merchants from encouraging customers to use cards that have lower processing fees, according to the report.

Representatives for Visa and MasterCard were not able to be reached for comment outside regular U.S. business hours.