WASHINGTON (Reuters) - Contentious Internet traffic rules facing a vote next week are likely to be adopted without radically veering from a proposal unveiled earlier in the month, telecommunications policy analysts said on Wednesday.

The Federal Communications Commission will vote on December 21 on whether to adopt regulations that ban the blocking of lawful traffic but allow Internet service providers to ration Web traffic on their networks.

The proposal laid out two weeks ago by FCC Chairman Julius Genachowski was met with concern from the other members of the FCC, putting in question the likelihood of winning over a majority of the five-member FCC.

The two Republican commissioners have objected to FCC action on Internet rules, saying the Internet is best able to thrive in the absence of regulation. And Genachowski’s two fellow Democrats on the panel could withhold support from any measure they view as too weak.

But analysts said commissioners Mignon Clyburn and Michael Copps, the Democrats on the panel, are more likely to consider it in the majority’s interest to move ahead with so-called net neutrality rules.

“There aren’t really any better options for Copps and Clyburn than to support the chairman, despite their preference for tougher rules,” said Paul Gallant, an analyst with MF Global.

“After the November elections, the chairman’s room to maneuver on net neutrality got a lot narrower,” he added.

Net neutrality rules would determine whether high-speed Internet providers should be allowed to block or slow information or charge websites for a “fast lane” to reach users more quickly.

Genachowski’s proposal is more flexible for wireless broadband, acknowledging that wireless is at an earlier stage of development than terrestrial Internet service.

High-speed and mobile Internet providers like Comcast Corp, Verizon Communications and AT&T Inc are likely to oppose any regulations that seek to go beyond Genachowski’s initial proposal.

“Our sense is an order likely will be approved, with some modifications, but not radical changes, to the draft, given the tightrope the FCC leadership appears to be walking,” Stifel Nicolaus analysts said in a research note.

Stifel Nicolaus is particularly plugged in to FCC developments, with analyst Rebecca Arbogast having previously been a division chief at the agency.

A possible tweak of Genachowski’s initial proposal could include clearer language against paid prioritization, Stifel Nicolaus analysts said, but strengthening the rules much further could prompt legal challenges from companies.

“Party loyalty will trump some of the policy differences,” Medley Global Advisors analyst Jeffrey Silva said of Copps and Clyburn’s potential reasons not to defect from the chairman.

Strengthening rules for wireless carriers beyond anti-blocking and transparency provisions, which Clyburn has supported, would probably be a deal-breaker for industry support of the regulations, Silva said.

“There’s not a lot of room to tinker with the compromise that’s been struck without threatening the compromise,” Silva said.

Even if the rules are adopted, lawmakers are likely to challenge the rules, as Republicans have been vocal that they oppose any FCC action geared at governing the Internet.