WASHINGTON, May 21 (Reuters) - Apple said Tuesday it plans to ask a U.S. judge to dismiss a lawsuit filed by the Justice Department and 15 states in March that alleged the iPhone maker monopolized the smartphone market, hurt smaller rivals and drove up prices.

In a letter to U.S. District Judge Julien X. Neals, 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. (Reporting by David Shepardson)