U.S. regulators have sued Qualcomm Inc., alleging that the San Diego company violated antitrust law.

The Federal Trade Commission filed the suit Jan. 17 in federal court in San Jose.

Qualcomm (Nasdaq: QCOM) issued a statement saying it planned to vigorously contest the complaint and defend its business practices.

“Qualcomm believes the complaint is based on a flawed legal theory, a lack of economic support and significant misconceptions about the mobile technology industry,” the company said in its statement. Qualcomm also said that the commission’s decision was not unanimous, pointing to a dissenting statement issued by Commissioner Maureen Ohlhausen.

Qualcomm shares closed Tuesday at $64.35, having lost 3.78 percent of their value. The Nasdaq as a whole was down less than 1 percent.

The San Diego business makes semiconductors and develops wireless communications technology, which it licenses to the rest of the industry.

A little more than two years ago, Qualcomm reported in its quarterly securities filing that the Federal Trade Commission was investigating its licensing business, including the question of whether Qualcomm breached its promise to license its technology on a fair, reasonable and nondiscriminatory basis (also known as FRAND). The FTC notified Qualcomm of the investigation in September of 2014. Qualcomm reported the matter in its November securities filing.

The news follows Qualcomm’s Dec. 27 announcement that South Korean regulators plan to fine the company $865 million for alleged anticompetitive behavior. Qualcomm said it would fight the charges.

Chinese antitrust regulators went after Qualcomm in late 2013, alleging anticompetitive behavior. Qualcomm settled the matter by paying a $975 million fine in February 2015, and rewriting its license terms for Chinese companies that use its technology.

The business plans to report first quarter financial results on Jan. 25.