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.

Visa shares fell 3% on Tuesday after a report said the U.S. Department of Justice plans to file a lawsuit against the world's largest payment processor, alleging it illegally monopolized the country's debit-card market.

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