(Reuters) - U.S. telecommunications regulators will vote on Thursday on whether to formally propose new "net neutrality" rules that may let Internet service providers charge content companies for faster and more reliable delivery of their traffic to users.

Federal Communications Commission Chairman Tom Wheeler has come under fire from consumer advocates and technology companies for proposing to allow some "commercially reasonable" deals where content companies could pay broadband providers to prioritize traffic on their networks.

Critics worry the rules would create "fast lanes" for companies that pay up and mean slower traffic for others, although Wheeler has pledged to prevent "acts to divide the Internet between 'haves' and 'have nots.'"

Some 200 activists have said they plan to protest at the FCC on Thursday, joining a few hard core critics who have camped outside the agency for a week. Consumer advocates were also mobilizing Internet users to protest online on blogs and through social media.

Those advocates want the FCC to reclassify Internet providers as utilities, like telephone companies, rather than as the less-regulated information services they are now. That move is opposed by broadband companies and Republicans, both in Congress and at the FCC.

Opponents, including House of Representatives Speaker John Boehner and CEOs of major Internet providers, told Wheeler that stricter regulations would throw the industry into legal limbo, discourage investment in network infrastructure and still not prevent pay-for-priority deals.

House Democrats have come out on both sides of the reclassification issue in recent communications to Wheeler.

More than 100 technology companies, including Google Inc and Facebook Inc, have spoken out against allowing pay-for-priority, although have not called for reclassification.

Wheeler's proposal reaches the tentative conclusion that some pay-for-priority deals may be allowed, but asks whether the FCC should presume "some or all" such deals are illegal, according to an FCC official briefed on the proposal. It also asks whether the FCC should instead consider reclassification or other net neutrality proposals.

The two Republican FCC commissioners are expected to vote against Wheeler's proposal. Wheeler's two fellow Democrats have both expressed misgivings about the plan, but are likely to vote

to launch the process and open it up to public comment.

The FCC will also vote on Thursday on rules for the sale of highly valuable low-frequency airwaves to wireless carriers. Those rules are expected to restrict how much the largest two providers, Verizon and AT&T, can buy.

(Reporting by Alina Selyukh. Editing by Ros Krasny and Andre Grenon)