WASHINGTON -- As more people use their Internet connection to watch movies and TV shows, fears have grown that broadband providers such as AT&T and Comcast will become online gatekeepers, using their control of Web pipes to block online video competitors like Netflix and protect their own pay-TV businesses.

That potential conflict is at the heart of a scheduled vote by the Federal Communications Commission on Tuesday on new rules to govern how broadband providers manage traffic over their networks, a pivotal moment in the debate over so-called network neutrality. The outcome could affect the ability of Silicon Valley giants such as Netflix and Apple to deliver movies and TV shows online for a fraction of the cost of a cable subscription.

FCC Chairman Julius Genachowski is attempting to settle a years-long battle that has pitted Web companies that want unfettered access to customers online against telecommunications giants that are loath to cede control over networks on which they've spent billions of dollars.

Genachowski's plan would bar broadband operators from blocking access to any legal website or application, or from transmitting traffic over the Web in a discriminatory way -- for example, by degrading the quality of an online video website that threatens to draw customers away from their own video or cable offerings.

But the plan would give broadband companies a green light to charge heavy Web users more than casual ones. People who stream a lot of Netflix or YouTube video to their laptops or TVs might pay more for their Internet service than those who only send e-mails or read news. Such "usage-based pricing" plans could give broadband companies a better return on investment and encourage them to beef up their networks, Genachowski said.

Genachowski's proposal, which he described in broad strokes during a speech this month but has declined to make public before the vote, has drawn mixed reaction from Silicon Valley. Several venture capitalists and entrepreneurs, including Craigslist's Craig Newmark, said it struck a sensible balance between keeping the Internet open to users and entrepreneurs without saddling broadband operators with burdensome rules that might dissuade them from upgrading networks.

"It doesn't have everything that everyone wanted," said Rey Ramsey, president and CEO of TechNet, a network of top Silicon Valley executives. "Down the road it will probably have to be updated, especially if there's any abuse. But it gives a little to get a little."

The big broadband providers, meanwhile, have held their fire, relieved that Genachowski backed off his earlier push to regulate them under the much stricter area of telecommunications law that governs telephone companies.

But the proposal has drawn fire from public interest groups and the Open Internet Coalition, which represents Silicon Valley interests such as Skype and eBay. They say it would give network operators too much room to charge some sites for faster speeds and leaving sites that don't pay extra in slower lanes. Such a system, they say, would put online startups that lack deep pockets to pay at a severe disadvantage, hurting innovation on the Web.

Critics also say any rules should apply equally to wired and wireless broadband; Genachowski's plan would mostly exempt wireless service from the new rules, except for a ban on blocking sites and a requirement that wireless operators disclose how they are managing traffic.

At the other end of the spectrum, Republican FCC members and GOP lawmakers say the Web has thrived in the absence of extensive government regulations and should be left alone. The proposed rules, Republican FCC Commissioner Meredith Attwell Baker said in a speech this month, would "micromanage the most dynamic and investment-friendly portion of our economy."

But Democrats outnumber Republicans 3 to 2 on the commission, and the big unknown is whether Democratic Commissioner Michael Copps, an advocate for strong rules, will settle for the compromise.

Uncertainty surrounds the debate because Genachowski is keeping the plan under wraps until the day of the vote as commissioners negotiate among themselves and make final tweaks. A spokeswoman said that process "has always been the case" at the commission and that no one has been denied a say in the long-running net-neutrality debate.

But critics such as Sascha Meinrath, an Internet expert at the New America Foundation think tank, said the process "makes a mockery" of Genachowski's pledge to run a transparent agency. TechNet's Ramsey did not go that far, but he agreed that the public should be privy to more details before such a critical vote.

"I would like to see something directly out there that everybody can review," he said. "We just have to continue to push for more openness."

Contact Mike Zapler at 202-662-8921.

THE FCC PROPOSAL
Would bar broadband operators from blocking access to particular websites or services.
Would give broadband companies a green light to charge heavy Web users more than casual ones. People who stream a lot of video might pay more than those who only send e-mails or read news.