The U.S. Justice Department on Tuesday sued Visa, the world’s biggest payments network, saying it propped up an illegal monopoly over debit payments by imposing “exclusionary” agreements on partners and smothering upstart firms.

Visa’s heft in the market has allowed it to pressure merchants into accepting its cards to avoid steep costs on billions of dollars of transactions, the DOJ says.

The Justice Department is accusing Visa of running a debit card monopoly that has hiked fees for American consumers and businesses.

The U.S. Justice Department has filed an antitrust lawsuit against Visa, alleging that the financial services behemoth uses its size and dominance to stifle competition in the debit card market

By Jody Godoy (Reuters) -Visa shares took a hit on Tuesday after the U.S. Department of Justice filed a lawsuit accusing it of violating antitrust law by suppressing competition by threatening merchants with high fees and paying off potential rivals.