The agency is considering a rule that would force the country’s largest wireless providers — AT&T and Verizon Wireless — to open their data networks to small and rural companies in the hopes of spurring competition and increasing access to wireless Internet services. The FCC may take a vote on the rule at its December meeting, industry sources tell POLITICO.

The debate is the latest skirmish in the larger battle over broadband reclassification. To impose the rule, the FCC would need to change the legal framework that governs broadband services — an idea pushed by net neutrality advocates but vehemently opposed by many Republicans and Internet providers.

Backers of the proposal, including T-Mobile, Sprint Nextel and MetroPCS, say they need to be able to “roam,” or access the larger national networks, when in areas where their own smaller networks don’t reach. That’s the only way they can ensure their customers can send data-heavy messages nationwide, they’ve told the FCC.

But AT&T and Verizon Wireless have come out swinging against the idea, saying the FCC doesn’t have the legal authority to force them to allow smaller competitors to piggyback on their multibillion-dollar networks.

Roaming issues are becoming increasingly important as wireless use becomes more prevalent. Data traffic will explode even more next year when the biggest carriers roll out their 4G networks, which is expected to drive data-heavy applications such as video-streaming via smart phones.

In April, the FCC ordered all cell phone companies to automatically allow wireless voice calls to roam on each other’s networks. The current proposal would do the same for data traffic, such as mobile Web browsing, which is growing so fast that it has already eclipsed voice traffic.

“Voice roaming and data roaming are clear economic substitutes and should be recognized as such by the commission,” the Rural Telecommunications Group wrote in a filing with the FCC late Tuesday. “In the eyes of the consumer, they are completely interchangeable.”

Enacting a data roaming rule would be politically expedient for FCC Chairman Julius Genachowski, who has faced legal setbacks in his quest to make wireless networks more open. Public interest groups complain that he is not making progress toward his promise of net neutrality on both wired and wireless networks.

But the FCC faces legal hurdles. The commission was able to require automatic roaming for voice calls because such traffic is considered a “common carrier” service. However, data traffic, or broadband, is considered an “information service,” to which the FCC does not have the explicit authority to impose common carrier rules.

AT&T and Verizon Wireless also argue that data traffic is a private radio service because it is not technically connected to the public switchboard, forbidding the FCC from applying the data-roaming mandate.

As a result, the FCC would have to reclassify broadband under a new legal framework before issuing a data roaming rule. That idea has been opposed by the FCC’s Republican commissioners as well as the big cell phone companies.

Public interest groups, including Free Press, Consumers Union and Public Knowledge, have had meetings at the FCC to push for mandatory data roaming. Doing so, they say, is the only way to increase wireless competition and keep prices reasonable for consumers.

Smaller carriers such as Cellular South, US Cellular and NTelos Wireless, many of whom operate in rural areas, say they can’t offer customers nationwide service without data roaming agreements. And they say the big providers charge too much money for such deals.

AT&T and Verizon Wireless argue they have roaming arrangements across the countries. They also worry that the FCC is trying to regulate their 4G networks before the services even come to market.

But disputes are cropping up. Last week, T-Mobile told the FCC that AT&T has refused to cooperate to reach a roaming agreement for its 3G network. AT&T refuted the claim, saying it would be willing to modify its existing agreement to include 3G. Verizon Wireless, meanwhile, says it has 65 roaming partners.

“Data roaming agreements are widely available and commonplace throughout the industry and should be negotiated on an individualized business-to-business basis without government intervention,” AT&T said in a filing with the FCC.

Eric Graham, Cellular South VP for strategic and government relations, says those agreements are too expensive for small companies to afford, effectively blocking them from the market.

“As we move to the next generation of technology, everything’s going to be data packets,” he told POLITICO. “It just makes sense for the FCC to do this.”