WASHINGTON (Reuters) - The U.S. Federal Communications Commission on Thursday launched an inquiry to examine the state of competition in the wireless industry, taking a step that could lead to probes of other sectors.

The FCC issued a notice of inquiry as part of a congressionally mandated annual assessment of the industry which is dominated by Verizon Wireless, AT&T Inc, Sprint Nextel Corp and T-Mobile, a unit of Deutsche Telekom AG.

Verizon Wireless is a joint venture between Verizon Communications Inc and Vodafone Group Plc.

The inquiry comes as the FCC is in the midst of examining exclusive deals between handset makers and carriers, such as Apple Inc's popular iPhone whose sole U.S. service provider is AT&T.

Exclusive deals are common among the biggest carriers but have recently faced strong opposition from rural carriers which say they lack the clout to make deals to carry the most popular phones.

FCC Chairman Julius Genachowski said the agency is seeking data on how competition affects consumers. He also said the wireless inquiry could lay the foundation for future questions in other sectors such as cable and broadband.

"I hope the new wireless competition report will help set a standard for fact-based, analytically deep analysis of the mobile industry," Genachowski said during an open meeting with a full slate of commissioners.

"And we will continue to apply such an analysis to all of the other competition and industry reports produced throughout the commission," he said.

(Reporting by John Poirier, Editing by Maureen Bavdek and Matthew Lewis)