In a letter to U.S. District Judge Julien X. Neals in New Jersey, Apple said "far from being a monopolist, Apple faces fierce competition from well-established rivals, and the complaint fails to allege that Apple has the ability to charge supra-competitive prices or restrict output in the alleged smartphone markets."

Apple said the complaint should be dismissed on a number of grounds. In the letter to the judge, Apple argues that the DOJ relies on a new "theory of antitrust liability that no court has recognized."

The Justice Department, which did not immediately comment on Tuesday, said earlier that Apple charges as much as $1,599 for an iPhone and makes a larger profit than any other companies in the industry. Officials also said Apple charges various business partners - from software developers to credit card companies and even its rivals such as Alphabet's Google - behind the scenes in ways that ultimately raise prices for consumers and drive up Apple's profit.

Apple rejected the government's contentions that the iPhone has kept consumers "locked in" to the devices. "Someone unhappy with Apple’s limitations has every incentive to switch to competitor platforms that ostensibly do not have those limitations," the letter said.

The Justice Department has said Apple was forcing consumers to pay more.

"Consumers should not have to pay higher prices because companies violate the antitrust laws," Attorney General Merrick Garland said in March. "If left unchallenged, Apple will only continue to strengthen its smartphone monopoly."